Center of population

, with a mean distance of convert|5000|km|sigfig=1|sp=us. Its antipodal point is correspondingly the "farthest" point from everyone on earth, and is located in the South Pacific near 15000|km|sp=us.

In demographics, the center of population of a region is the geographical point nearest to all the inhabitants of that region, on average.

Determination

Centers of population are usually computed by minimizing a population-weighted average of a distance metric. In other words, for some place P, the distance from P to a list of populated places is computed, and the distance to each populated place from P is weighted by the population of that place. The choice of P for which such a weighted average has the lowest value is held to be the center of population for the particular list of populated places used.

In practice, the person or agency doing the calculation decides whether to represent the area of interest in two-dimensional or three-dimensional space, and also the specific function to use for computing distances. For the particular case of flat maps, the center of population could also be defined as a center of mass (centroid) of the population of the area of interest.

Decisions are also made on the granularity (i.e., the "coarseness") of the population data, depending on population density patterns or other factors. For instance, the center of population of all the cities in a country may be different from the center of population of all the states (or provinces, or other subdivisions) in the same country. Different methods may yield different results.

Practical uses for finding the center of population include locating possible sites for forward capitals, such as Brasilia, Astana or Austin. Practical selection of a new site for a capital is a complex problem that depends also on population density patterns and transportation networks.

World

It is important to use a culturally neutral method when dealing with the entire world. As described in [http://www.ined.fr/fichier/t_publication/141/publi_pdf2_pop_and_soc_english_368.pdf] , the solution methodology deals only with the globe, and not with a two-dimensional projection of the Earth's surface. As a result, the answer is independent of which map projection is used or where it is centered. As described above, the exact location of the center of population will depend on both the granularity of the population data used, and the distance metric. With geodesic distances as the metric, and a granularity of convert|1000|km|sigfig=1|sp=us, meaning that two population centers within 1000 km of each other are treated as part of a larger common population center of intermediate location, the world's center of population is found to lie "at the crossroads between China, India, Pakistan and Tajikistan", with an average distance of convert|5200|km|sigfig=2|sp=us to all humans [http://www.ined.fr/fichier/t_publication/141/publi_pdf2_pop_and_soc_english_368.pdf] . The data used in the reference support this result to only a precision of a few hundred kilometers, hence the exact location is not known.

By country

Australia

Australia has not seen its population centroid move drastically since the creation of the country. In 1911, the centroid was in central New South Wales; in 1996, it was only slightly farther northwest. Fact|date=June 2008

The center of population for Bangladesh is close to Dhaka. Fact|date=June 2008

In 1993, the mean population center of Canada was found to be in the Township of Laxton, Digby and Longford, Victoria County, Fact|date=June 2008 now part of the city of Kawartha Lakes, Ontario.

Finland

In Finland, the center of population is located in the municipality of Hauho. Fact|date=June 2008 It is moving slightly to the west and south every year because people are moving out of the periphery areas of northern and eastern Finland.

Great Britain

The center of population in Great Britain did not move much in the 20th century. In 1901, it was in Rodsley, Derbyshire and in 1911 in Longford. In 1971 it was at Newhall, South Derbyshire and in 2000, it was in Appleby Parva, Leicestershire. Fact|date=June 2008

Japan

The center of population of Japan is in Gifu Prefecture, almost directly north of Nagoya city, and has been moving East South East for the past few decades. [ [http://www.stat.go.jp/data/kokusei/topics/topics22.htm Our Country's Center of Population (我が国の人口重心)] ] More recently, the only large regions in Japan with significant population growth have been in Greater Nagoya and Greater Tokyo.

Thailand

For Thailand, the center of population lies in the central plains area northwest of Bangkok. Fact|date=June 2008

USA

The mean center of United States population has been calculated for each U.S. Census since 1790. If the United States map were perfectly balanced on a point, this point would be its physical centroid. Currently this point is located in Phelps County, Missouri, in the east-central part of the state. However, when Washington, D.C. was chosen as the federal capital of the United States in 1790, the center of the U.S. population was in Kent County, Maryland, a mere convert|47|mi east-northeast of the new capital. For example, a congressman from Los Angeles must today travel inordinately far to work in the capital, whereas a congressman from Maryland or Virginia could easily drive to Washington, D.C.

The mean center of United States population has progressed westward and, since 1930, southwesterly. This reflects the population drift over the last two centuries. The southwest drift reflects the rise of major populations across Texas, Fact|date=June 2008 the exponential growth of Las Vegas, Fact|date=June 2008 and the rise of Los Angeles, Fact|date=June 2008 which became the second-largest American metro area, surpassing Chicago.

Median centers of population

A median center of population can be used to show where the median east vs west person lives. A person living near Louisville, Kentucky has about half of the US population living north of him and half of the US population living south of him. This measure is meaningful only along the specific coordinate axes (north-south and east-west).

Recently, the Center for the Study of Global Christianity in Massachusetts declared that the world's Christian "Center of Gravity" was located in Timbuktu, Mali. According to their definition of "Center of Gravity," half of all Christians live west of Timbuktu and half live south of Timbuktu. Presumably they had chosen the International Date Line to differentiate eastern from western people.

Sources

* Bellone F. and Cunningham R. (1993). "All Roads Lead to... Laxton, Digby and Longford." Statistics Canada 1991 Census Short Articles Series.

References

* [http://www.aph.gov.au/library/pubs/rp/1999-2000/2000rp09.htm#Figure15 Australian parliamentary research paper with map of population centroids] .
* [http://www.applebymagna.org.uk/population_centre.htm Site promoting Appleby Parva as centre of Great Britain]
* [http://www.census.gov/geo/www/cenpop/statecenters.txt Population centers of each U.S. state, 2000] (United States Census Bureau)

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