document_title: Mount St. Helens

question_text: when was the last time mount st helens erupted before 1980

text: Mount St. Helens

text: Geographic setting and description

text: General

text: Mount St. Helens is 34 miles (55 km) west of Mount Adams, in the western part of the Cascade Range. These "sister and brother" volcanic mountains are approximately 50 miles (80 km) from Mount Rainier, the highest of Cascade volcanoes. Mount Hood, the nearest major volcanic peak in Oregon, is 60 miles (100 km) southeast of Mount St. Helens.

text: Mount St. Helens is geologically young compared with the other major Cascade volcanoes. It formed only within the past 40,000 years, and the pre-1980 summit cone began rising about 2,200 years ago.[5] The volcano is considered the most active in the Cascades within the Holocene epoch (the last 10,000 or so years).[6]

text: Prior to the 1980 eruption, Mount St. Helens was the fifth-highest peak in Washington. It stood out prominently from surrounding hills because of the symmetry and extensive snow and ice cover of the pre-1980 summit cone, earning it the nickname "Fuji-san of America".[7] The peak rose more than 5,000 feet (1,500 m) above its base, where the lower flanks merge with adjacent ridges. The mountain is 6 miles (9.7 km) across at its base, which is at an elevation of 4,400 feet (1,300 m) on the northeastern side and 4,000 feet (1,200 m) elsewhere. At the pre-eruption tree line, the width of the cone was 4 miles (6.4 km).

text: Streams that originate on the volcano enter three main river systems: the Toutle River on the north and northwest, the Kalama River on the west, and the Lewis River on the south and east. The streams are fed by abundant rain and snow. The average annual rainfall is 140 inches (3,600 mm), and the snow pack on the mountain's upper slopes can reach 16 feet (4.9 m).[8] The Lewis River is impounded by three dams for hydroelectric power generation. The southern and eastern sides of the volcano drain into an upstream impoundment, the Swift Reservoir, which is directly south of the volcano's peak.

text: Although Mount St. Helens is in Skamania County, Washington, access routes to the mountain run through Cowlitz County to the west. State Route 504, locally known as the Spirit Lake Memorial Highway, connects with Interstate 5 at Exit 49, 34 miles (55 km) to the west of the mountain. That north–south highway skirts the low-lying cities of Castle Rock, Longview and Kelso along the Cowlitz River, and passes through the Vancouver, Washington–Portland, Oregon metropolitan area less than 50 miles (80 km) to the southwest. The community nearest the volcano is Cougar, Washington, in the Lewis River valley 11 miles (18 km) south-southwest of the peak. Gifford Pinchot National Forest surrounds Mount St. Helens.

text: Crater Glacier and other new rock glaciers

text: During the winter of 1980–1981, a new glacier appeared. Now officially named Crater Glacier, it was formerly known as the Tulutson Glacier. Shadowed by the crater walls and fed by heavy snowfall and repeated snow avalanches, it grew rapidly (14 feet (4.3 m) per year in thickness). By 2004, it covered about 0.36 square miles (0.93 km2), and was divided by the dome into a western and eastern lobe. Typically, by late summer, the glacier looks dark from rockfall from the crater walls and ash from eruptions. As of 2006, the ice had an average thickness of 300 feet (100 m) and a maximum of 650 feet (200 m), nearly as deep as the much older and larger Carbon Glacier of Mount Rainier. The ice is all post–1980, making the glacier very young geologically. However, the volume of the new glacier is about the same as all the pre–1980 glaciers combined.[10][11][12][13][14]

text: With the recent volcanic activity starting in 2004, the glacier lobes were pushed aside and upward by the growth of new volcanic domes. The surface of the glacier, once mostly without crevasses, turned into a chaotic jumble of icefalls heavily criss-crossed with crevasses and seracs caused by movement of the crater floor.[15] The new domes have almost separated the Crater Glacier into an eastern and western lobe. Despite the volcanic activity, the termini of the glacier have still advanced, with a slight advance on the western lobe and a more considerable advance on the more shaded eastern lobe. Due to the advance, two lobes of the glacier joined together in late May 2008 and thus the glacier completely surrounds the lava domes.[15][16][17] In addition, since 2004, new glaciers have formed on the crater wall above Crater Glacier feeding rock and ice onto its surface below; there are two rock glaciers to the north of the eastern lobe of Crater Glacier.[18] Crater Glacier is the only known advancing glacier in the contiguous United States.[19]

text: Geologic history

text: Ancestral stages of eruptive activity

text: The early eruptive stages of Mount St. Helens are known as the "Ape Canyon Stage" (around 40,000–35,000 years ago), the "Cougar Stage" (ca. 20,000–18,000 years ago), and the "Swift Creek Stage" (roughly 13,000–8,000 years ago).[20] The modern period, since about 2500 BCE, is called the "Spirit Lake Stage". Collectively, the pre–Spirit Lake stages are known as the "ancestral stages". The ancestral and modern stages differ primarily in the composition of the erupted lavas; ancestral lavas consisted of a characteristic mixture of dacite and andesite, while modern lava is very diverse (ranging from olivine basalt to andesite and dacite).[21]

text: St. Helens started its growth in the Pleistocene 37,600 years ago, during the Ape Canyon stage, with dacite and andesite eruptions of hot pumice and ash.[21] 36,000 years ago a large mudflow cascaded down the volcano;[21] mudflows were significant forces in all of St. Helens' eruptive cycles. The Ape Canyon eruptive period ended around 35,000 years ago and was followed by 17,000 years of relative quiet. Parts of this ancestral cone were fragmented and transported by glaciers 14,000 to 18,000 years ago during the last glacial period of the current ice age.[21]

text: The second eruptive period, the Cougar Stage, started 20,000 years ago and lasted for 2,000 years.[21] Pyroclastic flows of hot pumice and ash along with dome growth occurred during this period. Another 5,000 years of dormancy followed, only to be upset by the beginning of the Swift Creek eruptive period, typified by pyroclastic flows, dome growth and blanketing of the countryside with tephra. Swift Creek ended 8,000 years ago.

text: Smith Creek and Pine Creek eruptive periods

text: A dormancy of about 4,000 years was broken around 2500 BCE with the start of the Smith Creek eruptive period, when eruptions of large amounts of ash and yellowish-brown pumice covered thousands of square miles. An eruption in 1900 BCE was the largest known eruption from St. Helens during the Holocene epoch, judged by the volume of one of the tephra layers from that period. This eruptive period lasted until about 1600 BCE and left 18 inches (46 cm) deep deposits of material 50 miles (80 km) distant in what is now Mt. Rainier National Park. Trace deposits have been found as far northeast as Banff National Park in Alberta, and as far southeast as eastern Oregon.[22] All told there may have been up to 2.5 cubic miles (10 km3) of material ejected in this cycle.[22] Some 400 years of dormancy followed.

text: St. Helens came alive again around 1200 BCE — the Pine Creek eruptive period.[22] This lasted until about 800 BCE and was characterized by smaller-volume eruptions. Numerous dense, nearly red hot pyroclastic flows sped down St. Helens' flanks and came to rest in nearby valleys. A large mudflow partly filled 40 miles (64 km) of the Lewis River valley sometime between 1000 BCE and 500 BCE.

text: Castle Creek and Sugar Bowl eruptive periods

text: The next eruptive period, the Castle Creek period, began about 400 BCE, and is characterized by a change in composition of St. Helens' lava, with the addition of olivine and basalt.[23] The pre-1980 summit cone started to form during the Castle Creek period. Significant lava flows in addition to the previously much more common fragmented and pulverized lavas and rocks (tephra) distinguished this period. Large lava flows of andesite and basalt covered parts of the mountain, including one around the year 100 BCE that traveled all the way into the Lewis and Kalama river valleys.[23] Others, such as Cave Basalt (known for its system of lava tubes), flowed up to 9 miles (14 km) from their vents.[23] During the first century, mudflows moved 30 miles (50 km) down the Toutle and Kalama river valleys and may have reached the Columbia River. Another 400 years of dormancy ensued.

text: The Sugar Bowl eruptive period was short and markedly different from other periods in Mount St. Helens history. It produced the only unequivocal laterally directed blast known from Mount St. Helens before the 1980 eruptions.[24] During Sugar Bowl time, the volcano first erupted quietly to produce a dome, then erupted violently at least twice producing a small volume of tephra, directed-blast deposits, pyroclastic flows, and lahars.[24]

text: Kalama and Goat Rocks eruptive periods

text: Roughly 700 years of dormancy were broken in about 1480, when large amounts of pale gray dacite pumice and ash started to erupt, beginning the Kalama period. The eruption in 1480 was several times larger than the May 18, 1980, eruption.[24] In 1482, another large eruption rivaling the 1980 eruption in volume is known to have occurred.[24] Ash and pumice piled 6 miles (9.7 km) northeast of the volcano to a thickness of 3 feet (0.9 m); 50 miles (80 km) away, the ash was 2 inches (5 cm) deep. Large pyroclastic flows and mudflows subsequently rushed down St. Helens' west flanks and into the Kalama River drainage system.

text: This 150-year period next saw the eruption of less silica-rich lava in the form of andesitic ash that formed at least eight alternating light- and dark-colored layers.[23] Blocky andesite lava then flowed from St. Helens' summit crater down the volcano's southeast flank.[23] Later, pyroclastic flows raced down over the andesite lava and into the Kalama River valley. It ended with the emplacement of a dacite dome several hundred feet (~200 m) high at the volcano's summit, which filled and overtopped an explosion crater already at the summit.[25] Large parts of the dome's sides broke away and mantled parts of the volcano's cone with talus. Lateral explosions excavated a notch in the southeast crater wall. St. Helens reached its greatest height and achieved its highly symmetrical form by the time the Kalama eruptive cycle ended, about 1647.[25] The volcano remained quiet for the next 150 years.

text: The 57-year eruptive period that started in 1800 was named after the Goat Rocks dome, and is the first time that both oral and written records exist.[25] Like the Kalama period, the Goat Rocks period started with an explosion of dacite tephra, followed by an andesite lava flow, and culminated with the emplacement of a dacite dome. The 1800 eruption probably rivalled the 1980 eruption in size, although it did not result in massive destruction of the cone. The ash drifted northeast over central and eastern Washington, northern Idaho, and western Montana. There were at least a dozen reported small eruptions of ash from 1831 to 1857, including a fairly large one in 1842. The vent was apparently at or near Goat Rocks on the northeast flank.[25] Goat Rocks dome was the site of the bulge in the 1980 eruption, and it was obliterated in the major eruption event on May 18, 1980 that destroyed the entire north face and top 1,300 feet (400 m) of the mountain.

text: Modern eruptive period

text: 1980 to 2001 activity

text: On March 20, 1980, Mount St. Helens experienced a magnitude 4.2 earthquake;[2] and, on March 27, steam venting started.[26] By the end of April, the north side of the mountain had started to bulge.[27] On May 18, a second earthquake, of magnitude 5.1, triggered a massive collapse of the north face of the mountain. It was the largest known debris avalanche in recorded history. The magma in St. Helens burst forth into a large-scale pyroclastic flow that flattened vegetation and buildings over 230 square miles (600 km2). More than 1.5 million metric tons of sulfur dioxide was released into the atmosphere.[28] On the Volcanic Explosivity Index scale, the eruption was rated a five, and categorized as a Plinian eruption.

text: The collapse of the northern flank of St. Helens mixed with ice, snow, and water to create lahars (volcanic mudflows). The lahars flowed many miles down the Toutle and Cowlitz Rivers, destroying bridges and lumber camps. A total of 3,900,000 cubic yards (3,000,000 m3) of material was transported 17 miles (27 km) south into the Columbia River by the mudflows.[29]

text: For more than nine hours, a vigorous plume of ash erupted, eventually reaching 12 to 16 miles (20 to 27 km) above sea level.[30] The plume moved eastward at an average speed of 60 miles per hour (100 km/h) with ash reaching Idaho by noon. Ashes from the eruption were found collecting on top of cars and roofs next morning, as far as the city of Edmonton in Alberta, Canada.

text: By about 5:30 p.m. on May 18, the vertical ash column declined in stature, and less severe outbursts continued through the night and for the next several days. The St. Helens May 18 eruption released 24 megatons of thermal energy;[3][31] it ejected more than 0.67 cubic miles (2.79 km3) of material.[3] The removal of the north side of the mountain reduced St. Helens' height by about 1,300 feet (400 m) and left a crater 1 mile (1.6 km) to 2 miles (3.2 km) wide and 0.5 miles (800 m) deep, with its north end open in a huge breach. The eruption killed 57 people, nearly 7,000 big game animals (deer, elk, and bear), and an estimated 12 million fish from a hatchery.[8] It destroyed or extensively damaged over 200 homes, 185 miles (298 km) of highway and 15 miles (24 km) of railways.[8]

text: Between 1980 and 1986, activity continued at Mount St. Helens, with a new lava dome forming in the crater. Numerous small explosions and dome-building eruptions occurred. From December 7, 1989, to January 6, 1990, and from November 5, 1990, to February 14, 1991, the mountain erupted with sometimes huge clouds of ash.[32]

text: 2004 to 2008 activity

text: Magma reached the surface of the volcano about October 11, 2004, resulting in the building of a new lava dome on the existing dome's south side. This new dome continued to grow throughout 2005 and into 2006. Several transient features were observed, such as a lava spine nicknamed the "whaleback," which comprised long shafts of solidified magma being extruded by the pressure of magma beneath. These features were fragile and broke down soon after they were formed. On July 2, 2005, the tip of the whaleback broke off, causing a rockfall that sent ash and dust several hundred meters into the air.[33]

text: Mount St. Helens showed significant activity on March 8, 2005, when a 36,000-foot (11,000 m) plume of steam and ash emerged—visible from Seattle.[34] This relatively minor eruption was a release of pressure consistent with ongoing dome building. The release was accompanied by a magnitude 2.5 earthquake.

text: Another feature to emerge from the dome was called the "fin" or "slab." Approximately half the size of a football field, the large, cooled volcanic rock was being forced upward as quickly as 6 ft (2 m) per day.[35][36] In mid-June 2006, the slab was crumbling in frequent rockfalls, although it was still being extruded. The height of the dome was 7,550 feet (2,300 m), still below the height reached in July 2005 when the whaleback collapsed.

text: On October 22, 2006, at 3:13 p.m. PST, a magnitude 3.5 earthquake broke loose Spine 7. The collapse and avalanche of the lava dome sent an ash plume 2,000 feet (600 m) over the western rim of the crater; the ash plume then rapidly dissipated.

text: On December 19, 2006, a large white plume of condensing steam was observed, leading some media people to assume there had been a small eruption. However, the Cascades Volcano Observatory of the USGS did not mention any significant ash plume.[37] The volcano was in continuous eruption from October 2004, but this eruption consisted in large part of a gradual extrusion of lava forming a dome in the crater.

text: On January 16, 2008, steam began seeping from a fracture on top of the lava dome. Associated seismic activity was the most noteworthy since 2004. Scientists suspended activities in the crater and the mountain flanks, but the risk of a major eruption was deemed low.[38] By the end of January, the eruption paused; no more lava was being extruded from the lava dome. On July 10, 2008, it was determined that the eruption had ended, after more than six months of no volcanic activity.[39]

text: Human history

text: Importance to Native Americans

text: American Indian lore contains numerous legends to explain the eruptions of Mount St. Helens and other Cascade volcanoes. The most famous of these is the Bridge of the Gods legend told by the Klickitat people. In their tale, the chief of all the gods and his two sons, Pahto (also called Klickitat) and Wy'east, traveled down the Columbia River from the Far North in search for a suitable area to settle.[40]

text: They came upon an area that is now called The Dalles and thought they had never seen a land so beautiful. The sons quarreled over the land, so to solve the dispute their father shot two arrows from his mighty bow — one to the north and the other to the south. Pahto followed the arrow to the north and settled there while Wy'east did the same for the arrow to the south. The chief of the gods then built the Bridge of the Gods, so his family could meet periodically.[40]

text: When the two sons of the chief of the gods fell in love with a beautiful maiden named Loowit, she could not choose between them. The two young chiefs fought over her, burying villages and forests in the process. The area was devastated and the earth shook so violently that the huge bridge fell into the river, creating the cascades of the Columbia River Gorge.[41]

text: For punishment, the chief of the gods struck down each of the lovers and transformed them into great mountains where they fell. Wy'east, with his head lifted in pride, became the volcano known today as Mount Hood. Pahto, with his head bent toward his fallen love, was turned into Mount Adams. The fair Loowit became Mount St. Helens, known to the Klickitats as Louwala-Clough, which means "smoking or fire mountain" in their language (the Sahaptin called the mountain Loowit).[42]

text: The mountain is also of sacred importance to the Cowlitz and Yakama tribes that also historically lived in the area. They find the area above its tree line to be of exceptional spiritual significance, and the mountain (which they call "Lawetlat'la", roughly translated as "the smoker") features prominently in their creation myth, and in some of their songs and rituals. In recognition of this cultural significance, over 12,000 acres (4,900 ha) of the mountain (roughly bounded by the Loowit Trail) have been listed on the National Register of Historic Places.[43]

text: Other area tribal names for the mountain include "nšh´ák´" ("water coming out") from the Upper Chehalis, and "aka akn" ("snow mountain"), a Kiksht term.[43]

text: Exploration by Europeans

text: Royal Navy Commander George Vancouver and the officers of HMS Discovery made the Europeans' first recorded sighting of Mount St. Helens on May 19, 1792, while surveying the northern Pacific Ocean coast. Vancouver named the mountain for British diplomat Alleyne Fitzherbert, 1st Baron St Helens on October 20, 1792,[42][44] as it came into view when the Discovery passed into the mouth of the Columbia River.

text: Years later, explorers, traders, and missionaries heard reports of an erupting volcano in the area. Geologists and historians determined much later that the eruption took place in 1800, marking the beginning of the 57-year-long Goat Rocks Eruptive Period (see geology section).[25] Alarmed by the "dry snow," the Nespelem tribe of northeastern Washington danced and prayed rather than collecting food and suffered during that winter from starvation.[25]

text: In late 1805 and early 1806, members of the Lewis and Clark Expedition spotted Mount St. Helens from the Columbia River but did not report either an ongoing eruption or recent evidence of one.[45] They did however report the presence of quicksand and clogged channel conditions at the mouth of the Sandy River near Portland, suggesting an eruption by Mount Hood sometime in the previous decades.

text: In 1829 Hall J. Kelley led a campaign to rename the Cascade Range as the President's Range and also to rename each major Cascade mountain after a former President of the United States. In his scheme Mount St. Helens was to be renamed Mount Washington.[46]

text: European settlement and use of the area

text: The first authenticated eyewitness report of a volcanic eruption was made in March 1835 by Meredith Gairdner, while working for the Hudson's Bay Company stationed at Fort Vancouver.[47] He sent an account to the Edinburgh New Philosophical Journal, which published his letter in January 1836. James Dwight Dana of Yale University, while sailing with the United States Exploring Expedition, saw the quiescent peak from off the mouth of the Columbia River in 1841. Another member of the expedition later described "cellular basaltic lavas" at the mountain's base.[48]

text: In late fall or early winter of 1842, nearby settlers and missionaries witnessed the so-called "Great Eruption". This small-volume outburst created large ash clouds, and mild explosions followed for 15 years.[49] The eruptions of this period were likely phreatic (steam explosions). Josiah Parrish in Champoeg, Oregon witnessed Mount St. Helens in eruption on November 22, 1842. Ash from this eruption may have reached The Dalles, Oregon, 48 miles (80 km) southeast of the volcano.[6]

text: In October 1843, future California governor Peter H. Burnett recounted a story of an aboriginal American man who badly burned his foot and leg in lava or hot ash while hunting for deer. The likely apocryphal story went that the injured man sought treatment at Fort Vancouver, but the contemporary fort commissary steward, Napoleon McGilvery, disclaimed knowledge of the incident.[50] British lieutenant Henry J. Warre sketched the eruption in 1845, and two years later Canadian painter Paul Kane created watercolors of the gently smoking mountain. Warre's work showed erupting material from a vent about a third of the way down from the summit on the mountain's west or northwest side (possibly at Goat Rocks), and one of Kane's field sketches shows smoke emanating from about the same location.[51]

text: On April 17, 1857, the Republican, a Steilacoom, Washington, newspaper, reported that "Mount St. Helens, or some other mount to the southward, is seen ... to be in a state of eruption".[52] The lack of a significant ash layer associated with this event indicates that it was a small eruption. This was the first reported volcanic activity since 1854.[52]

text: Before the 1980 eruption, Spirit Lake offered year-round recreational activities. In the summer there was boating, swimming, and camping, while in the winter there was skiing.

text: Human impact from the 1980 eruption

text: Fifty-seven people were killed during the eruption.[53] Had the eruption occurred one day later, when loggers would have been at work, rather than on a Sunday, the death toll could have been much higher.[8]

text: 83-year-old Harry R. Truman, who had lived near the mountain for 54 years, became famous when he decided not to evacuate before the impending eruption, despite repeated pleas by local authorities. His body was never found after the eruption.

text: Another victim of the eruption was 30-year-old volcanologist David A. Johnston, who was stationed on the nearby Coldwater Ridge. Moments before his position was hit by the pyroclastic flow, Johnston radioed his famous last words: "Vancouver! Vancouver! This is it!"[54] Johnston's body was never found.

text: U.S. President Jimmy Carter surveyed the damage and said, "Someone said this area looked like a moonscape. But the moon looks more like a golf course compared to what's up there."[55] A film crew, led by Seattle filmmaker Otto Seiber, was dropped by helicopter on St. Helens on May 23 to document the destruction. Their compasses, however, spun in circles and they quickly became lost. A second eruption occurred on May 25, but the crew survived and was rescued two days later by National Guard helicopter pilots. Their film, The Eruption of Mount St. Helens, later became a popular documentary.

text: Protection and later history

text: In 1982, President Ronald Reagan and the U.S. Congress established the Mount St. Helens National Volcanic Monument, a 110,000 acres (45,000 ha) area around the mountain and within the Gifford Pinchot National Forest.[56]

text: Following the 1980 eruption, the area was left to gradually return to its natural state. In 1987, the U.S. Forest Service reopened the mountain to climbing. It remained open until 2004 when renewed activity caused the closure of the area around the mountain (see Geological history section above for more details).

text: Most notable was the closure of the Monitor Ridge trail, which previously let up to 100 permitted hikers per day climb to the summit. On July 21, 2006, the mountain was again opened to climbers.[57] In February 2010, a climber died after falling from the rim into the crater.[58]

text: The mountain is now circled by the Loowit Trail at elevations of 4000–4900 feet. The northern segment of the trail from the South Fork Toutle River on the west to Windy Pass on the east is a restricted zone where camping, biking, pets, fires, and off-trail excursions are all prohibited.[59][60]

text: Climbing and recreation

text: Mount St. Helens is a popular climbing destination for both beginning and experienced mountaineers. The peak is climbed year-round, although it is more often climbed from late spring through early fall. All routes include sections of steep, rugged terrain.[61] A permit system has been in place for climbers since 1987. A climbing permit is required year-round for anyone who will be above 4,800 feet (1,500 m) on the slopes of Mount St. Helens.[62]

text: The standard hiking/mountaineering route in the warmer months is the Monitor Ridge Route, which starts at the Climbers Bivouac. This is the most popular and crowded route to the summit in the summer and gains about 4,600 feet (1,400 m) in approximately 5 miles (8.0 km) to reach the crater rim.[63] Although strenuous, it is considered non-technical climb that involves some scrambling. Most climbers complete the round trip in 7 to 12 hours.[64]

text: The Worm Flows Route is considered the standard winter route on Mount St. Helens, as it is the most direct route to the summit. The route gains about 5,700 feet (1,700 m) in elevation over about 6 miles (9.7 km) from trailhead to summit but does not demand the technical climbing that some other Cascade peaks like Mount Rainier do. The "Worm Flows" part of the route name refers to the rocky lava flows that surround the route.[65] This route can be accessed via the Marble Mountain Sno-Park and the Swift Ski Trail.[66]


document_title: Econometrics

question_text: what is the meaning of blue in econometrics

root

text: Econometrics

text: Basic models: linear regression[edit]

text: The basic tool for econometrics is the multiple linear regression model.[9] In modern econometrics, other statistical tools are frequently used, but linear regression is still the most frequently used starting point for an analysis.[9] Estimating a linear regression on two variables can be visualized as fitting a line through data points representing paired values of the independent and dependent variables.

tag: p

text:
For example, consider Okun's law, which relates GDP growth to the unemployment rate. This relationship is represented in a linear regression where the change in unemployment rate (

Δ

Unemployment

{\displaystyle \Delta \ {\text{Unemployment}}}

) is a function of an intercept (

β

0

{\displaystyle \beta _{0}}

), a given value of GDP growth multiplied by a slope coefficient

β

1

{\displaystyle \beta _{1}}

 and an error term,

ε

{\displaystyle \varepsilon }

:

text:
The unknown parameters

β

0

{\displaystyle \beta _{0}}

 and

β

1

{\displaystyle \beta _{1}}

 can be estimated. Here

β

1

{\displaystyle \beta _{1}}

 is estimated to be −1.77 and

β

0

{\displaystyle \beta _{0}}

 is estimated to be 0.83. This means that if GDP growth increased by one percentage point, the unemployment rate would be predicted to drop by 1.77 points. The model could then be tested for statistical significance as to whether an increase in growth is associated with a decrease in the unemployment, as hypothesized. If the estimate of

β

1

{\displaystyle \beta _{1}}

 were not significantly different from 0, the test would fail to find evidence that changes in the growth rate and unemployment rate were related. The variance in a prediction of the dependent variable (unemployment) as a function of the independent variable (GDP growth) is given in polynomial least squares.

text: Theory[edit]

text: Econometric theory uses statistical theory and mathematical statistics to evaluate and develop econometric methods.[10][11] Econometricians try to find estimators that have desirable statistical properties including unbiasedness, efficiency, and consistency. An estimator is unbiased if its expected value is the true value of the parameter; it is consistent if it converges to the true value as sample size gets larger, and it is efficient if the estimator has lower standard error than other unbiased estimators for a given sample size. Ordinary least squares (OLS) is often used for estimation since it provides the BLUE or "best linear unbiased estimator" (where "best" means most efficient, unbiased estimator) given the Gauss-Markov assumptions. When these assumptions are violated or other statistical properties are desired, other estimation techniques such as maximum likelihood estimation, generalized method of moments, or generalized least squares are used. Estimators that incorporate prior beliefs are advocated by those who favor Bayesian statistics over traditional, classical or "frequentist" approaches.

text: Methods[edit]

text: Applied econometrics uses theoretical econometrics and real-world data for assessing economic theories, developing econometric models, analyzing economic history, and forecasting.[12]

text: Econometrics may use standard statistical models to study economic questions, but most often they are with observational data, rather than in controlled experiments.[13] In this, the design of observational studies in econometrics is similar to the design of studies in other observational disciplines, such as astronomy, epidemiology, sociology and political science. Analysis of data from an observational study is guided by the study protocol, although exploratory data analysis may be useful for generating new hypotheses.[14] Economics often analyzes systems of equations and inequalities, such as supply and demand hypothesized to be in equilibrium. Consequently, the field of econometrics has developed methods for identification and estimation of simultaneous-equation models. These methods are analogous to methods used in other areas of science, such as the field of system identification in systems analysis and control theory. Such methods may allow researchers to estimate models and investigate their empirical consequences, without directly manipulating the system.

text: One of the fundamental statistical methods used by econometricians is regression analysis.[15] Regression methods are important in econometrics because economists typically cannot use controlled experiments. Econometricians often seek illuminating natural experiments in the absence of evidence from controlled experiments. Observational data may be subject to omitted-variable bias and a list of other problems that must be addressed using causal analysis of simultaneous-equation models.[16]

text: Example[edit]

text: A simple example of a relationship in econometrics from the field of labor economics is:

text:
This example assumes that the natural logarithm of a person's wage is a linear function of the number of years of education that person has acquired. The parameter

β

1

{\displaystyle \beta _{1}}

 measures the increase in the natural log of the wage attributable to one more year of education. The term

ε

{\displaystyle \varepsilon }

 is a random variable representing all other factors that may have direct influence on wage. The econometric goal is to estimate the parameters,

β

0

 and

β

1

{\displaystyle \beta _{0}{\mbox{ and }}\beta _{1}}

 under specific assumptions about the random variable

ε

{\displaystyle \varepsilon }

. For example, if

ε

{\displaystyle \varepsilon }

 is uncorrelated with years of education, then the equation can be estimated with ordinary least squares.

text: If the researcher could randomly assign people to different levels of education, the data set thus generated would allow estimation of the effect of changes in years of education on wages. In reality, those experiments cannot be conducted. Instead, the econometrician observes the years of education of and the wages paid to people who differ along many dimensions. Given this kind of data, the estimated coefficient on Years of Education in the equation above reflects both the effect of education on wages and the effect of other variables on wages, if those other variables were correlated with education. For example, people born in certain places may have higher wages and higher levels of education. Unless the econometrician controls for place of birth in the above equation, the effect of birthplace on wages may be falsely attributed to the effect of education on wages.

text:
The most obvious way to control for birthplace is to include a measure of the effect of birthplace in the equation above. Exclusion of birthplace, together with the assumption that

ϵ

{\displaystyle \epsilon }

 is uncorrelated with education produces a misspecified model. Another technique is to include in the equation additional set of measured covariates which are not instrumental variables, yet render

β

1

{\displaystyle \beta _{1}}

 identifiable.[17] An overview of econometric methods used to study this problem were provided by Card (1999).[18]

text: Journals[edit]

text: The main journals that publish work in econometrics are Econometrica, the Journal of Econometrics, the Review of Economics and Statistics, Econometric Theory, the Journal of Applied Econometrics, Econometric Reviews, the Econometrics Journal,[19] Applied Econometrics and International Development, and the Journal of Business & Economic Statistics.

text: Limitations and criticisms[edit]

text: Like other forms of statistical analysis, badly specified econometric models may show a spurious relationship where two variables are correlated but causally unrelated. In a study of the use of econometrics in major economics journals, McCloskey concluded that some economists report p-values (following the Fisherian tradition of tests of significance of point null-hypotheses) and neglect concerns of type II errors; some economists fail to report estimates of the size of effects (apart from statistical significance) and to discuss their economic importance. She also argues that some economists also fail to use economic reasoning for model selection, especially for deciding which variables to include in a regression.[20][21]

text: In some cases, economic variables cannot be experimentally manipulated as treatments randomly assigned to subjects.[22] In such cases, economists rely on observational studies, often using data sets with many strongly associated covariates, resulting in enormous numbers of models with similar explanatory ability but different covariates and regression estimates. Regarding the plurality of models compatible with observational data-sets, Edward Leamer urged that "professionals ... properly withhold belief until an inference can be shown to be adequately insensitive to the choice of assumptions".[23]


document_title: African empires

question_text: an empire in west africa that became a powerful state

text: African empires

text: Sahelian kingdoms[edit]

text: The Sahelian kingdoms were a series of medieval empires centred on the sahel, the area of grasslands south of the Sahara.

text:
The first major state to rise in this region was the Ghana Empire (Wagadu). The name Ghana, often used by historians, was the regnal title given to the ruler of the Wagadu empire.[8] Centered in what is today Senegal and Mauritania, it was the first to benefit from the introduction of gold mining. Ghana dominated the region between about 750 and 1078. Smaller states in the region at this time included Takrur to the west, the Malinke kingdom of Mali to the south, and the Songhai Empire centred on Gao to the east.
When Ghana collapsed in the face of invasion from the Almoravids, a series of brief kingdoms followed, notably that of the Sosso (Susu); after 1235, the Mali Empire rose to dominate the region. Located on the Niger River to the west of Ghana in what is today Niger and Mali, it reached its peak in the 1350s, but had lost control of a number of vassal states by 1400.
The most powerful of these states was the Songhai Empire, which expanded rapidly beginning with king Sonni Ali in the 1460s. By 1500, it had risen to stretch from Cameroon to the Maghreb, the largest state in African history. It too was quite short-lived and collapsed in 1591 as a result of Moroccan musketry.
Far to the east, on Lake Chad, the state of Kanem-Bornu, founded as Kanem in the 9th century, now rose to greater preeminence in the central Sahel region. To their west, the loosely united Hausa city-states became dominant. These two states coexisted uneasily, but were quite stable.
In 1810, the Sokoto Caliphate rose and conquered the Hausa, creating a more centralized state. It and Kanem-Bornu would continue to exist until the arrival of Europeans, when both states would fall and the region would be divided between France and Great Britain.
Jolof Empire (1350–1889)

tag: ul

text: Empires of 15th–19th century Africa[edit]

text: From the 15th century until the final Scramble for Africa in the late 19th century a number of empires were also established south of the Sahel, especially in West Africa.

text: West Africa[edit]

text: The West African empires of this period peaked in power in the late 18th century, paralleling the peak of the Atlantic slave trade. These empires implemented a culture of permanent warfare in order to generate the required numbers of captives required to satisfy the demand for slaves by the European colonies. With the gradual abolition of slavery in the European colonial empires during the 19th century, slave trade again became less lucrative and the West African empires entered a period of decline, and mostly collapsed by the end of the 19th century.[9]

text:
The Nok Civilization is considered to be one of the most advanced ancient sub-Saharan civilizations in African history. Beginning some time around 1500 BC, it was largely concentrated in what is now Nigeria but produced some of the first sub-Saharan iron smelting and terracotta architecture. Mysteriously died out around 200 AD.
The Kingdom of Nri (1043–1911) was the West African medieval state of the Nri-Igbo, a subgroup of the Igbo people, and is the oldest kingdom in Nigeria. The Kingdom of Nri was unusual in the history of world government in that its leader exercised no military power over his subjects. The kingdom existed as a sphere of religious and political influence over much of Igboland, and was administered by a priest-king called the eze Nri. The eze Nri managed trade and diplomacy on behalf of the Igbo people, and was the possessor of divine authority in religious matters.
The Oyo Empire (1400–1895) was a West African empire of what is today western Nigeria. The empire was established by the Yoruba in the 15th century and grew to become one of the largest West African states. It rose to prominence through wealth gained from trade and its possession of a powerful cavalry. The Oyo Empire was the most politically important state in the region from the mid-17th to the late 18th century, holding sway not only over other Yoruba states, but also over the Fon kingdom of Dahomey (located in the state now known as the Republic of Benin).
Benin Empire (1440–1897), a pre-colonial African state of modern Nigeria.
Kaabu Empire (1537–1867), a Mandinka Kingdom of Senegambia (centered on modern northeastern Guinea-Bissau but extending into Casamance, Senegal) that rose to prominence in the region thanks to its origins as a former province of the Mali Empire. After the decline of the Mali Empire, Kaabu became an independent kingdom.
Aro Confederacy (1690–1902), a trading union orchestrated by the Igbo subgroup, the Aro people, centered in Arochukwu in present-day Southeastern Nigeria.
Bonoman (11th century–19th century), earliest known Akan state. Gold trading and Kola nut trading with Northern Neighbors brought wealth and prosperity to Akan creators of this state. Culture influenced much of modern Akan culture.
Ashanti Empire (1701–1894), a pre-colonial Akan West African state of what is now the Ashanti Region in Ghana. The empire stretched from central Ghana to present day Togo and Côte d'Ivoire, bordered by the Dagomba kingdom to the north and Dahomey to the east. Today, the Ashanti monarchy continues as one of the constitutionally protected, sub-national traditional states within the Republic of Ghana.
Various states by Akan people (11th century–19th century)
Kong Empire (1710–1898) centered in north eastern Côte d'Ivoire that also encompassed much of present-day Burkina Faso.
Bamana Empire (1712–1896) based at Ségou, now in Mali. It was ruled by the Kulubali or Coulibaly dynasty established c. 1640 by Fa Sine also known as Biton-si-u. The empire existed as a centralized state from 1712 to the 1861 invasion of Toucouleur conqueror El Hadj Umar Tall.
Sokoto Caliphate (1804–1903), an Islamic empire in Nigeria, led by the Sultan of Sokoto, Sa’adu Abubakar. Founded during the Fulani Jihad in the early 19th century, it was one of the most powerful empires in sub-Saharan Africa prior to European conquest and colonization. The caliphate remained extant through the colonial period and afterwards, though with reduced power.
Wassoulou Empire (1878–1898), a short-lived empire of built from the conquests of Dyula ruler Samori Ture and destroyed by the French colonial army.

text: Great Lakes[edit]

text:
An Empire of Kitara in the area of the African Great Lakes has long been treated as a historical entity, but is now mostly considered an unhistorical narrative created as a response to the dawn of rule under the Lwo empire. The latter is the sole historical record of an organized Nilotic migration into the area.[10]
The Buganda (1300–present), home of the Buganda people of Uganda
The medieval Swahili city-states

text: Congo[edit]

text:
The Kongo Kingdom (1400–1888) was a quasi-imperial state as is evident by the number of peoples and kingdoms that paid it tribute. If not for the large amount of text written by the EssiKongo that repeatedly called themselves a kingdom, they would be listed as the "Kongo Empire".
The Luba Empire (1585–1885) arose in the marshy grasslands of the Upemba Depression in what is now southern Democratic Republic of Congo.
Lunda Empire (1660–1887) in what is now the Democratic Republic of Congo, north-eastern Angola and northwestern Zambia. Its central state was in Katanga.

text: Southern Africa[edit]

text: The Mutapa Empire or Empire of Great Zimbabwe (1450–1629) was a medieval kingdom located between the Zambezi and Limpopo rivers of Southern Africa in the modern states of Zimbabwe and Mozambique. Remnants of the historical capital are found in the ruins of Great Zimbabwe.

text:
Zulu Kingdom
Maravi Empire or Marawi or Merowi or Merowe/ Meroe Empire. Not to be confused with Ancient Meroe.
Kingdom of Mapungubwe

text: North Africa[edit]

text: Ancient North African Empires[edit]

text: Pre-Islamic empires of North Africa:

text:
Kingdom of Kerma (2500–1500 BC)
Ancient Egypt (3100–650 BC)
Kingdom of Kush (1070–350 AD)

Nobatia (350–650 AD)
Makuria (340–1312 AD)
Alodia (??? AD–1504 AD)

Ancient Carthage (575–146 BC)

text: African Empires[edit]

text:
In Algeria:

Banu Ifran dynasty (830–1040)
Zirid dynasty (947–1090)
Hammadid dynasty (1014–1152)
Almohad caliphate (1145–1244)

In Morocco:

Idrisid dynasty (789–974)
Almoravid dynasty (1061–1145)
Almohad dynasty (1145–1244)
Marinid dynasty (1244–1465)
Wattasid dynasty (1471–1554)
Saadi dynasty (1554–1659)
Alaouite dynasty (1666–present)

In Tunisia:

Fatimid dynasty (Tunisian period) (910–969)
Zirid dynasty (973–1148)
Hafsid dynasty (1229–1574)

In Egypt:

Fatimid dynasty (Egyptian period) (969–1171)
Ayyubid dynasty (1171–1254)
Mamluk dynasty (1250–1517)

In Sudan:

The Sennar Sultanate (1502–1821) was a sultanate in the north of Sudan. It was named Funj after the ethnic group of its dynasty or Sinnar (or Sennar) after its capital, which ruled a substantial area of the Sudan region.

text: Horn of Africa[edit]

text:
Ancient land of Punt (2500 BC)
Ancient Barbara/Barbaroi cities and states mentioned in the Periplus of the Erythraean Sea (1st century).

Opone/Xāfūn (1000 BC – 5th century AD)
Mundus/Xīs
Mosylon/Bōsāso
Malao/Berbera
Nikon/Būr Gābo
Sarapion/Muqdisho

Kingdom of Aksum (1st century – 9th century)
Kingdom of Bazin (9th century)
Kingdom of Belgin (9th century)
Kingdom of Jarin (9th century)
Kingdom of Qita'a (9th century)
Kingdom of Nagash (9th century)
Kingdom of Tankish (9th century)
Sultanate of Mogadishu (10th century – 16th century)
Ethiopian Empire (1137–1974)

Zagwe dynasty (1137–1270)
Solomonic dynasty (1270–1974)

Sultanate of Ifat (1285–1415)
Warsangali Sultanate (1298–1960)
Ajuran Sultanate (1300s–1700s)
Adal Sultanate (1415–1555)
Sultanate of Harar (1526–1577)
Emirate of Harar (1647–1887)
Sultanate of the Geledi (late 17th century – late 19th century)
Majeerteen Sultanate (mid-18th century – early 20th century)
Sultanate of Aussa (1734–present)
Kingdom of Gomma (early 1800s–1886)
Kingdom of Jimma (1830–1932)
Kingdom of Gumma (1840–1902)
Sultanate of Hobyo (1880s–1920s)
Dervish state (1896–1920)

text: Comparison[edit]

text: Vansina (1962) discusses the classification of Sub-Saharan African kingdoms, mostly of Central, South and East Africa, with some additional data on West African (Sahelian) kingdoms distinguishing five types, by decreasing centralization of power:

text:
Despotic kingdoms: Kingdoms where the king controls the internal and external affairs directly. Examples are Ruanda, Nkore, Soga and Kongo in the 16th century
Regal kingdoms: Kingdoms where the king controls the external affairs directly, and the internal affairs via a system of overseers. The king and his chiefs belong to the same clans or lineages.
Incorporative kingdoms: Kingdoms where the king only controls only the external affairs with no permanent administrative links between him and the chiefs of the provinces. The hereditary chiefdoms of the provinces were left undisturbed after conquest. Examples are the Bamileke, Lunda, Luba, Lozi.
Aristocratic kingdoms: The only link between central authority and the provinces is payment of tribute. These kingdoms are morphologically intermediate between regal kingdoms and federations. This type is rather common in Africa, examples including the Kongo of the 17th century, the Cazembe, Luapula, Kuba, Ngonde, Mlanje, Ha, Zinza and Chagga states of the 18th century
Federations: Kingdoms (such as the Ashanti Union) where the external affairs are regulated by a council of elders headed by the king, who is simply primus inter pares.

tag: ol

text: Sources[edit]

text:
Hunwick, John O. (2003). Timbuktu and the Songhay Empire: Al-Saʻdī's Taʼrīkh al-sūdān Down to 1613 and other Contemporary Documents. Leiden: Brill Academic Publishers. pp. 488 Pages. ISBN 90-04-12822-0.
J. Vansina, A Comparison of African Kingdoms, Africa: Journal of the International African Institute (1962), pp. 324–335.
Turchin, Peter and Jonathan M. Adams and Thomas D. Hall: "East-West Orientation of Historical Empires and Modern States", Journal of World-Systems Research, Vol. XII, No. II, 2006


document_title: Multiple birth

question_text: what do you call 5 siblings born at the same time

text: Multiple birth

text: Terminology[edit]

text: Terms used for multiple births or the genetic relationships of their offspring:

text:
Monozygotic – multiple (typically two) fetuses produced by the splitting of a single zygote
Polyzygotic – multiple fetuses produced by two or more zygotes:

text:
Dizygotic – multiple (typically two) fetuses produced by two zygotes
Trizygotic – three or more fetuses produced by three zygotes

text: Terms used for the number of offspring in a multiple birth:

text:
Two offspring - twins
Three offspring - triplets
Four offspring - quadruplets
Five offspring - quintuplets
Six offspring - sextuplets
Seven offspring - septuplets
Eight offspring - octuplets
Nine offspring - nonuplets
Ten offspring - decuplets

text: See List of multiple births.

text: Human multiple births[edit]

text: In humans, the average length of pregnancy (two weeks fewer than gestation) is 38 weeks with a single fetus. This average decreases for each additional fetus: to thirty-six weeks for twin births, thirty-two weeks for triplets, and thirty weeks for quadruplets. With the decreasing gestation time, the risks from immaturity at birth and subsequent viability increase with the size of the sibling group. Only as of the twentieth century have more than four all survived infancy.

text: Recent history has also seen increasing numbers of multiple births. In the United States, it has been estimated that by 2011, 36% of twin births and 78% of triplet and higher-order births resulted from conception by assisted reproductive technology.[1]

text: Twins[edit]

text: Twins are by far the most common form of multiple births in humans. The U.S. Centers for Disease Control and Prevention report more than 132,000 sets of twins out of 3.9 million births of all kinds each year, about 3.4%, or 1 in 30.[2]

text: Triplets[edit]

text: Identical triplets come from a monozygotic pregnancy, three fetuses from one egg. The most common set, strictly fraternal triplets, comes from a polyzygotic pregnancy of three eggs. Between these types, triplets that include an identical (monozygotic) pair of siblings plus a fraternal sibling are the result of a dizygotic pregnancy, where one zygote divides into two fetuses and the other doesn't.

text: Triplets are far less common than twins, according to the U.S. Centers for Disease Control and Prevention, accounting for only about 4300 sets in 3.9 million births, just a little more than 0.1%, or 1 in 1000.[2] According to the American Society of Reproductive Medicine, only about 10% of these are identical triplets: about 1 in ten thousand.[2] Nevertheless, only 4 sets of identical triplets were reported in the U.S. during 2015, about one in a million.[2] According to Victor Khouzami, Chairman of Obstetrics at Greater Baltimore Medical Center, "No one really knows the incidence".[2]

text: Identical triplets or quadruplets are very rare and result when the original fertilized egg splits and then one of the resultant cells splits again (for triplets) or, even more rarely, a further split occurs (for quadruplets). The odds of having identical triplets is unclear. News articles and other non-scientific organizations give odds from one in 60,000 to one in 200 million pregnancies.[2][4][5][6][7][8]

text: Quadruplets[edit]

text:
Quadruplets are much rarer than twins or triplets. As of 2007, there were approximately 3500 sets recorded worldwide. Quadruplet births are becoming increasingly common due to fertility treatments. There are around 70 sets of all-identical quadruplets worldwide. Many sets of quadruplets contain a mixture of identical and fraternal siblings, such as three identical and one fraternal, two identical and two fraternal, or two pairs of identicals. One famous set of identical quadruplets was the Genain quadruplets, all of whom developed schizophrenia.
Quadruplets are sometimes referred to as "quads" in Britain.[9]

text: Quintuplets[edit]

text: Quintuplets occur naturally in 1 in 55,000,000 births.[10] The first quintuplets known to survive infancy were the all-female Canadian Dionne Quintuplets, born in 1934. Quintuplets are sometimes referred to as "quins" in the UK and "quints" in North America.[11]

text: Sextuplets[edit]

text: Born in Liverpool, England on 18 November 1983, the Walton sextuplets were the world's first all-female surviving sextuplets, and the world's fourth known set of surviving sextuplets. Another well-known set of sextuplets is the Gosselin sextuplets, born May 10, 2004 in Hershey, Pennsylvania.[12] Reality television shows called Jon & Kate Plus 8 and later Kate Plus 8 have chronicled the lives of these sextuplets.

text: Very high-order multiple births[edit]

text: In 1997, the McCaughey septuplets were born in Carlisle, Iowa. Multiple births of as many as eight babies have been born alive, the first set on record to the Chukwu family in Texas in 1998; one died and seven survived. In 2009, a second set, the Suleman octuplets, were born in Bellflower, California.[13][14] The most recent report that all were still alive shortly before their fifth birthday.[15]

text: There have been a few sets of nonuplets (nine) in which a few babies were born alive, though none lived longer than a few days. There have been cases of human pregnancies that started out with ten, eleven, twelve or fifteen fetuses, but no instances of live births.  The pregnancies of the 10, 11 and 15 fetuses have all resulted from fertility medications and assisted reproductive technology (ART). However, there has been one documented case when 12 fetuses were conceived naturally.[16][not in citation given]

text: Causes and frequency[edit]

text: The examples and perspective in this article deal primarily with North America and do not represent a worldwide view of the subject. You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. (December 2010) (Learn how and when to remove this template message)

tag: table

text: The frequency of N multiple births from natural pregnancies has been given as approximately 1:89N-1 (Hellin's law) and as about 1:80N-1.[17] This gives:

text:
1:89 (= 1.1%) or 1:80 (= 1.25%) for twins
1:892 (= 1:7921, about 0.013%) or 1:802 (= 1:6400) for triplets
1:893 (= approx. 0.000142%, less than 1:700,000) or 1:803 for quadruplets

text: North American dizygotic twinning occurs about once in 83 conceptions, and triplets about once in 8000 conceptions. US figures for 2010 were:[18][19]

text:
Twins, 132,562, 3.31%
Triplets, 5,503, 0.14%
Quadruplets, 313, 0.0078%
Quintuplets and more, 37, 0.00092%

text: Human multiple births can occur either naturally (the woman ovulates multiple eggs or the fertilized egg splits into two) or as the result of infertility treatments such as IVF (several embryos are often transferred to compensate for lower quality) or fertility drugs (which can cause multiple eggs to mature in one ovulatory cycle).

text: For reasons that are not yet known, the older a woman is, the more likely she is to have a multiple birth naturally. It is theorized that this is due to the higher level of follicle-stimulating hormone that older women sometimes have as their ovaries respond more slowly to FSH stimulation.[20]

text: The number of multiple births has increased over the last decade. For example, in Canada between 1979 and 1999, the number of multiple birth babies increased 35%. Before the advent of ovulation-stimulating drugs, triplets were quite rare (approximately 1 in 8000 births) and higher-order births much rarer still.[citation needed] Much of the increase can probably be attributed to the impact of fertility treatments, such as in-vitro fertilization. Younger patients who undergo treatment with fertility medication containing artificial FSH, followed by intrauterine insemination, are particularly at risk for multiple births of higher order.

text: Certain factors appear to increase the likelihood that a woman will naturally conceive multiples. These include:

text:
mother's age: women over 35 are more likely to have multiples than younger women[21]
mother's use of fertility drugs: approximately 35% of pregnancies arising through the use of fertility treatments such as IVF involve more than one child

text: The increasing use of fertility drugs and consequent increased rate of multiple births has made the phenomenon of multiples more frequent and hence more visible. In 2004 the birth of sextuplets, six children, to Pennsylvania couple Kate and Jon Gosselin helped them to launch their television series, originally Jon & Kate Plus 8 and (following their divorce) Kate Plus 8, which became the highest-rated show on the TLC network.

text: Risks[edit]

text: Premature birth and low birth weight[edit]

text: Babies born from multiple-birth pregnancies are much more likely to result in premature birth than those from single pregnancies. 51% of twins and 91% of triplets are born preterm, compared to 9.4% in singletons.[22] 14% of twins and 41% of triplets are even born very preterm, compared to 1.7% in singletons.[22]

text: At present, there is no way to stop twins being born early.[23] In women with single pregnancies drugs called betamimetics can relax the muscles of the uterus and delay birth.[24] Giving betamimetics can give more time to give steroids, for the baby’s lung development, or to transfer the mother to a hospital with a special care unit.[24]

text: However, there is not enough evidence to say whether or not women with twin pregnancies should be given oral betamimetics to reduce the risk of preterm birth.[23] In some studies betamimetics have reduced the rate of preterm labour in twin pregnancies however the studies are too small to draw any solid conclusions.[23] Likewise, putting a stitch in the neck of the womb (a cervical suture) to prevent premature birth has not been shown to work in women carrying more than one baby due to the small sample sizes in the studies.[25]

text: The preterm births also result in multiples tending to have a lower birth weight compared to singletons.

text: Some evidence[who?] indicates that only 1.10% of singletons are born with a very low birth weight and 10.12% twins and 31.88% triplets were found to be born with very low birth weight.  This study[who?] was conducted by looking at the statistics from the U.S. Natality Files (5).

text: Among the exceptions are the Kupresak triplets of Mississauga, Ontario, Canada; their combined weight at birth in 2008, of 17 lbs, 2.7 ounces, set a world record.[26]

text: Cerebral palsy[edit]

text: Cerebral palsy is more common among multiple births than single births, being 2.3 per 1,000 survivors in singletons, 13 in twins, and 45 in triplets in North West England.[27] This is likely a side effect of premature birth and low birth weight.

text: Incomplete separation[edit]

text: Multiples may be monochorionic, sharing the same chorion, with resultant risk of twin-to-twin transfusion syndrome. Monochorionic multiples may even be monoamniotic, sharing the same amniotic sac, resulting in risk of umbilical cord compression and nuchal cord. In very rare cases, there may be conjoined twins, possibly impairing function of internal organs.

text: Mortality rate (stillbirth)[edit]

text:
Multiples are also known to have a higher mortality rate.  It is more common for multiple births to be stillborn, while for singletons the risk is not as high.  A literary review on multiple pregnancies shows a study done on one set each of septuplets and octuplets, two sets of sextuplets, 8 sets of quintuplets, 17 sets of quadruplets, and 228 sets of triplets.  By doing this study, Hammond found that the mean gestational age (how many weeks when birthed) at birth was 33.4 weeks for triplets and 31 weeks for quadruplets. This shows that stillbirth happens usually 3–5 weeks before the woman reaches full term and also that for sextuplets or higher it almost always ends in death of the fetuses.[28]
Though multiples are at a greater risk of being stillborn, there is inconclusive evidence whether the actual mortality rate is higher in multiples than in singletons.

text: Prevention in IVF[edit]

text: Today many multiple pregnancies are the result of in vitro fertilisation (IVF). In a study in 1997 of 2,173 embryo transfers performed as part of in vitro fertilisation (IVF), 34% were successfully delivered pregnancies.[29] The overall multiple pregnancy rate was 31.3% (24.7% twins, 5.8% triplets, and .08% quadruplets).[29] Because IVFs are producing more multiples, a number of efforts are being made to reduce the risk of multiple births- specifically triplets or more. Medical practitioners are doing this by limiting the number of embryos per embryo transfer to one or two. That way, the risks for the mother and fetuses are decreased.

text: The appropriate number of embryos to be transferred depends on the age of the woman, whether it is the first, second or third full IVF cycle attempt and whether there are top-quality embryos available. According to a guideline from The National Institute for Health and Care Excellence (NICE) in 2013, the number of embryos transferred in a cycle should be chosen as in following table:[30]

text:
Age
Attempt no.
Embryos transferred

<37 years
1st
1

2nd
1 if top-quality

3rd
No more than 2

37–39 years
1st & 2nd
1 if top-quality

2 if not top-quality

3rd
No more than 2

40–42 years

2

text: Also, it is recommended to use single embryo transfer in all situations if a top-quality blastocyst is available.[30]

text: Management[edit]

text: Bed rest has not been found to change outcomes and therefore is not generally recommended outside of a research study.[31]

text: Selective reduction[edit]

text: Selective reduction is the termination of one or more, but not all, of the fetuses in a multiple pregnancy. This is often done in pregnancies with multiple gestations to increase the likelihood that one child may live a healthy life. Armour[32] reported a loss rate of 5.4% in a review of 1,000 cases of selective reduction.  Fifteen percent of the losses occurred within 4 weeks of the procedures and more than 50% occurred after 8 weeks. This suggests that the reduction was successful at reducing the embryos from multiple gestations to single.

text: Though selective reduction seems to be effective, mothers of multiples who undergo this procedure are at a higher risk of miscarrying compared to that of an unreduced multiple pregnancy.  A study done by looking at 158 pregnant women who underwent selective reduction from higher order multiples to twins showed that the mother had a 10.6% chance of miscarriage. Mothers of twin pregnancies without reduction only had a 9.5% chance of miscarriage.  A study by Antsaklis[33] showed a small increase in mortality for reduced twin pregnancies versus unreduced twin pregnancies.

text: However, there is a lack of good quality research on the risks and benefits of selective reduction procedures.[34] Many parents often find the suggestion of selective termination upsetting particularly if the pregnancy is a result of IVF or they have had difficulty getting pregnant in the past. Background, religious or personal beliefs can all play a part in effecting whether parents want to go through with the procedure and could be the reason why research in this area is scarce.[34]

text: Competition among fertility clinics does not appear to increase rates of multiple births from fertility treatment by promoting more aggressive embryo transfer decisions.[35]

text: Care in pregnancy[edit]

text:
Women with a multiple pregnancy are usually seen more regularly by midwives or doctors than those with singleton pregnancies because of the higher risks of complications.[36] However, there is currently no evidence to suggest that specialised antenatal services produce better outcomes for mother or babies than ‘normal’ antenatal care.
[37]

text: Nutrition[edit]

text: As preterm birth is such a risk for women with multiple pregnancies, it has been suggested that these women should be encouraged to follow a high-calorie diet to increase the birth weights of the babies. Evidence around this subject is not yet good enough to advise women to do this because the long term effects of the high-calorie diets on the mother are not known.[38]

text: Cesarean section or vaginal delivery[edit]

text: A study in 2013 involving 106 participating centers in 25 countries came to the conclusion that, in a twin pregnancy of a gestational age between 32 weeks 0 days and 38 weeks 6 days, and the first twin is in cephalic presentation, planned Cesarean section does not significantly decrease or increase the risk of fetal or neonatal death or serious neonatal disability, as compared with planned vaginal delivery.[39] In this study, 44% of the women planned for vaginal delivery still ended up having Cesarean section for unplanned reasons such as pregnancy complications. In comparison, it has been estimated that 75% of twin pregnancies in the United States were delivered by Cesarean section in 2008.[40] Also in comparison, the rate of Cesarean section for all pregnancies in the general population varies between 40% and 14%.[41]

text: Fetal position (the way the babies are lying in the womb) usually determines if they are delivered by caesarean section or vaginally. A review of good quality research on this subject found that if the twin that will be born first (i.e. is lowest in the womb) is head down there is no good evidence that caesarean section will be safer than a vaginal birth for the mother or babies.[42]

text: Monoamniotic twins (twins that form after the splitting of a fertilised egg and share the same amniotic fluid sac) are at more risk of complications than twins that have their own sacs. There is also insufficient evidence around whether to deliver the babies early by caesarean section or to wait for labour to start naturally while running checks on the babies’ wellbeing.[43] The birth of this type of twins should therefore be decided with the mother and her family and should take into account the need for good neonatal care services.[44]

text: Cesarean delivery is needed when first twin is in non cephalic presentation or when it is a monoamniotic twin pregnancy.

text: Neonatal intensive care[edit]

text: Multiple-birth infants are usually admitted to neonatal intensive care immediately after being born. The records for all the triplet pregnancies managed and delivered from 1992-1996 were looked over to see what the neonatal statistics were.  Kaufman[45] found from reviewing these files that during a five-year period, 55 triplet pregnancies, which is 165 babies, were delivered.  Of the 165 babies 149 were admitted to neonatal intensive care after the delivery.

text: Society and culture[edit]

text: Insurance coverage[edit]

text: A study by the U.S. Agency for Healthcare Research and Quality found that, in 2011, pregnant women covered by private insurance in the United States were older and more likely to have multiple gestation than women covered by Medicaid.[46]

text: Cultural aspects[edit]

text: Certain cultures consider multiple births a portent of either good or evil.[47]

text: Mayan culture saw twins as a blessing, and was fascinated by the idea of two bodies looking alike. The Mayans used to believe that twins were one soul that had fragmented.[citation needed]

text: In Ancient Rome, the legend of the twin brothers who founded the city (Romulus and Remus) made the birth of twin boys a blessing, while twin girls were seen as an unlucky burden, since both would have to be provided with an expensive dowry at about the same time.

text: In Greek mythology, fraternal twins Castor and Polydeuces, and Heracles and Iphicles, are sons of two different fathers. One of the twins (Polydeuces, Heracles) is the illegitimate son of the god Zeus; his brother is the son of their mother's mortal husband. A similar pair of twin sisters are Helen (of Troy) and Clytemnestra (who are also sisters of Castor and Polydeuces). The theme occurs in other mythologies as well, and is called superfecundation.

text: In certain medieval European chivalric romances, such as Marie de France's Le Fresne, a woman cites a multiple birth (often to a lower-class woman) as proof of adultery on her part; while this may reflect a widespread belief, it is invariably treated as malicious slander, to be justly punished by the accuser having a multiple birth of her own, and the events of the romance are triggered by her attempt to hide one or more of the children.[48]  A similar effect occurs in the Knight of the Swan romance, in the Beatrix variants of the Swan-Children; her taunt is punished by giving birth to seven children at once, and her wicked mother-in-law returns her taunt before exposing the children.[49]


document_title: List of Heisman Trophy winners

question_text: who won the 2010 heisman trophy for college football

text: List of Heisman Trophy winners

text: Key[edit]

text:
*
First overall draft pick in the NFL Draft

†
Inducted into the Pro Football Hall of Fame

‡
First overall draft pick and inducted into the Pro Football Hall of Fame

text: List of Heisman Trophy winners[edit]

text:
Heisman Winners

Year
Image
Name
School
Position
Points
 % of Points Possible[15]
Class

1935

Berwanger, JayJay Berwanger*
Chicago
Halfback
84
43.08%
Senior

1936

Kelley, LarryLarry Kelley
Yale
End
219
36.41%
Senior

1937

Frank, ClintClint Frank
Yale
Halfback
524
32.89%
Senior

1938

O'Brien, DaveyDavey O'Brien
TCU
Quarterback
519
29.62%
Senior

1939

Kinnick, NileNile Kinnick
Iowa
Halfback/Quarterback
651
31.00%
Senior

1940

Harmon, TomTom Harmon*
Michigan
Halfback
1,303
54.29%
Senior

1941

Smith, BruceBruce Smith
Minnesota
Halfback
554
49.99%
Senior

1942

Sinkwich, FrankFrank Sinkwich*
Georgia
Halfback
1,059
56.15%
Senior

1943

Bertelli, AngeloAngelo Bertelli*
Notre Dame
Quarterback
648
64.80%
Senior

1944

Horvath, LesLes Horvath
Ohio State
Quarterback/Halfback
412
18.31%
Senior

1945

Blanchard, DocDoc Blanchard
Army
Fullback
860
33.81%
Junior

1946

Davis, GlennGlenn Davis
Army
Halfback
792
79.20%
Senior

1947

Lujack, JohnnyJohnny Lujack
Notre Dame
Quarterback
742
74.20%
Senior

1948

Walker, DoakDoak Walker†
SMU
Halfback
778
28.56%
Junior

1949

Hart, LeonLeon Hart*
Notre Dame
End
995
36.53%
Senior

1950

Janowicz, VicVic Janowicz
Ohio State
Halfback/Punter
633
22.03%
Junior

1951

—

Kazmaier, DickDick Kazmaier
Princeton
Halfback
1,777
60.01%
Senior

1952

Vessels, BillyBilly Vessels
Oklahoma
Halfback
525
14.32%
Senior

1953

Lattner, JohnnyJohnny Lattner
Notre Dame
Halfback
1,850
49.14%
Senior

1954

Ameche, AlanAlan Ameche
Wisconsin
Fullback
1,068
27.01%
Senior

1955

Cassady, HowardHoward Cassady
Ohio State
Halfback
2,219
55.87%
Senior

1956

—

Hornung, PaulPaul Hornung‡
Notre Dame
Quarterback
1,066
26.96%
Senior

1957

Crow, John DavidJohn David Crow
Texas A&M
Halfback
1,183
31.12%
Senior

1958

Dawkins, PetePete Dawkins
Army
Halfback
1,394
39.01%
Senior

1959

Cannon, BillyBilly Cannon*
LSU
Halfback
1,929
53.72%
Senior

1960

—

Bellino, JoeJoe Bellino
Navy
Halfback
1,793
52.89%
Senior

1961

Davis, ErnieErnie Davis*
Syracuse
Halfback/Linebacker/Fullback
824
25.18%
Senior

1962

—

Baker, TerryTerry Baker*
Oregon State
Quarterback
707
21.25%
Senior

1963

Staubach, RogerRoger Staubach†
Navy
Quarterback
1,860
55.21%
Junior

1964

Huarte, JohnJohn Huarte
Notre Dame
Quarterback
1,026
30.98%
Senior

1965

Garrett, MikeMike Garrett
USC
Halfback
926
26.61%
Senior

1966

Spurrier, SteveSteve Spurrier
Florida
Quarterback
1,679
48.25%
Senior

1967

—

Beban, GaryGary Beban
UCLA
Quarterback
1,968
63.50%
Senior

1968

Simpson, O. J.O. J. Simpson‡
USC
Halfback
2,853
80.64%
Senior

1969

—

Owens, SteveSteve Owens
Oklahoma
Fullback
1,488
40.92%
Senior

1970

Plunkett, JimJim Plunkett*
Stanford
Quarterback
2,229
58.78%
Senior

1971

—

Sullivan, PatPat Sullivan
Auburn
Quarterback
1,597
42.25%
Senior

1972

—

Rodgers, JohnnyJohnny Rodgers
Nebraska
Wide Receiver/Running back
1,310
38.75%
Senior

1973

—

Cappelletti, JohnJohn Cappelletti
Penn State
Running back
1,057
32.78%
Senior

1974

Griffin, ArchieArchie Griffin
Ohio State
Running back
1,920
59.53%
Junior

1975
Griffin, ArchieArchie Griffin
Ohio State
Running back
1,800
57.64%
Senior

1976

Dorsett, TonyTony Dorsett†
Pittsburgh
Running back
2,357
74.97%
Senior

1977

Campbell, EarlEarl Campbell‡
Texas
Running back
1,547
49.11%
Senior

1978

Sims, BillyBilly Sims*
Oklahoma
Running back
1,896
26.25%
Junior

1979

—

White, CharlesCharles White
USC
Running back
1,695
53.81%
Senior

1980

—

Rogers, GeorgeGeorge Rogers*
South Carolina
Running back
1,128
35.81%
Senior

1981

Allen, MarcusMarcus Allen†
USC
Running back
1,797
57.05%
Senior

1982

Walker, HerschelHerschel Walker
Georgia
Running back
1,926
61.14%
Junior

1983

—

Rozier, MikeMike Rozier
Nebraska
Running back
1,801
57.17%
Senior

1984

Flutie, DougDoug Flutie
Boston College
Quarterback
2,240
71.11%
Senior

1985

Jackson, BoBo Jackson*
Auburn
Running back
1,509
47.90%
Senior

1986

Testaverde, VinnyVinny Testaverde*
Miami
Quarterback
2,213
70.25%
Senior

1987

Brown, TimTim Brown†
Notre Dame
Wide receiver
1,442
45.78%
Senior

1988

Sanders, BarryBarry Sanders†
Oklahoma State
Running back
1,878
68.27%
Junior

1989

Ware, AndreAndre Ware
Houston
Quarterback
1,073
38.96%
Junior

1990

Detmer, TyTy Detmer
BYU
Quarterback
1,482
53.87%
Junior

1991

Howard, DesmondDesmond Howard
Michigan
Wide receiver/Punt returner
2,077
75.50%
Junior

1992

Torretta, GinoGino Torretta
Miami
Quarterback
1,400
50.84%
Senior

1993

Ward, CharlieCharlie Ward
Florida State
Quarterback
2,310
83.79%
Senior

1994

Salaam, RashaanRashaan Salaam
Colorado
Running back
1,743
63.15%
Junior

1995

George, EddieEddie George
Ohio State
Running back
1,460
52.84%
Senior

1996

Wuerffel, DannyDanny Wuerffel
Florida
Quarterback
1,363
49.38%
Senior

1997

Woodson, CharlesCharles Woodson
Michigan
Cornerback/Punt returner
1,815
65.69%
Junior

1998

Williams, RickyRicky Williams
Texas
Running back
2,355
85.23%
Senior

1999

Dayne, RonRon Dayne
Wisconsin
Running back
2,042
73.83%
Senior

2000

Weinke, ChrisChris Weinke
Florida State
Quarterback
1,628
58.86%
Senior

2001

—

Crouch, EricEric Crouch
Nebraska
Quarterback
770
27.75%
Senior

2002

Palmer, CarsonCarson Palmer*
USC
Quarterback
1,328
48.01%
Senior

2003

White, JasonJason White
Oklahoma
Quarterback
1,481
53.54%
Junior

2004

Leinart, MattMatt Leinart
USC
Quarterback
1,325
47.85%
Junior

2005
(vacated)

—

Reggie Bush
USC
Running Back
2,541
91.77%
Junior

2006

Smith, TroyTroy Smith
Ohio State
Quarterback
2,540
91.63%
Senior

2007

Tebow, TimTim Tebow
Florida
Quarterback
1,957
70.52%
Sophomore

2008

Bradford, SamSam Bradford*
Oklahoma
Quarterback
1,726
62.13%
Sophomore

2009

Ingram, Jr., MarkMark Ingram, Jr.
Alabama
Running back
1,304
46.99%
Sophomore

2010

Newton, CamCam Newton*
Auburn
Quarterback
2,263
81.55%
Junior

2011

Griffin III, RobertRobert Griffin III
Baylor
Quarterback
1,687
60.66%
Junior

2012

Manziel, JohnnyJohnny Manziel
Texas A&M
Quarterback
2,029
72.88%
Freshman

2013

Winston, JameisJameis Winston*
Florida State
Quarterback
2,205
79.12%
Freshman

2014

Mariota, MarcusMarcus Mariota
Oregon
Quarterback
2,534
90.92%
Junior

2015

Henry, DerrickDerrick Henry
Alabama
Running back
1,832
65.73%
Junior

2016

Jackson, LamarLamar Jackson
Louisville
Quarterback
2,144
79.50%
Sophomore

text: Trophies won by school[edit]

text: This is a list of the colleges and universities who have had a player win a Heisman trophy: Ohio State and Notre Dame are tied for the most trophies at 7 each (USC's 2005 award having been voluntarily forfeited). Ohio State has the distinction of the only two-time winner, Archie Griffin, leaving their total players to have won the trophy at six. In total, players from 39 different schools have won a Heisman Trophy, while 18 schools have more than one trophy.

text:
School
Trophies
held

Notre Dame
7

Ohio State
7

USC
6†

Oklahoma
5

Army
3

Auburn
3

Florida
3

Florida State
3

Michigan
3

Nebraska
3

Alabama
2

Georgia
2

Miami
2

Navy
2

Texas
2

Texas A&M
2

Wisconsin
2

Yale
2

Baylor
1

BYU
1

Boston College
1

Colorado
1

Chicago
1

Houston
1

Iowa
1

Louisville
1

LSU
1

Minnesota
1

Oklahoma State
1

Oregon
1

Oregon State
1

Penn State
1

Pittsburgh
1

Princeton
1

South Carolina
1

SMU
1

Stanford
1

Syracuse
1

TCU
1

UCLA
1

text: † The 2005 title was forfeited by Reggie Bush and is not tallied here.