[[Image:WorldCenterOfPopulation.png|thumb|400px|The
point on earth closest to everyone in the world on average is in
the northern part of South Asia (Hindu Kush), with a mean distance of
. Its antipodal point is correspondingly the *farthest* point from everyone on earth, and is located in the South Pacific near Easter Island, with a mean distance of .]]

In

demographics, the

**center of
population** (or

**population center**) of a
region is a geographical point that describes a centerpoint of the
region's population. There are several different ways of defining
such a "center point", leading to different geographical locations;
these are often confused.

## Definitions

Three commonly used definitions are:

- the
*mean center*, also known as the
*centroid* or *center of gravity*;
- the
*median center*, which is the
intersection of the median longitude and
median latitude;
- the
*geometric median*,
also known as *Weber point*, *Fermatâ€“Weber point*, or
*point of minimum aggregate travel*.

A further complication is caused by the curved shape of the Earth.
Different center points are obtained depending on whether the
center is computed in three-dimensional space, or restricted to the
curved surface, or computed using a flat

map projection.

### Mean center

The mean center, or centroid, is the point on which a rigid,
weightless map would balance perfectly, if the population is
represented as points of equal mass.

Mathematically, the centroid is the point to which the population
has the smallest possible

*sum of squared distances*. It is
easily found by taking the arithmetic

mean of
each coordinate. If defined in the three-dimensional space, the
centroid of points on the Earth's surface is actually inside the
Earth. This point could then be projected back to the surface.
Alternatively, one could define the centroid directly on a flat map
projection; this is, for example, the definition that the

US Census Bureau uses.

Contrary to a common misconception, the centroid does

*not*
minimize the average distance to the population. That property
belongs to the geometric median.

### Median center

The median center is the intersection of two perpendicular lines,
each of which divides the population into two equal halves.
Typically these two lines are chosen to be a latitude and a
longitude. In that case, this center is easily found by taking
separately the

medians of the population's
latitude and longitude coordinates.

### Geometric median

The geometric median is the point to which the population has the
smallest possible

*sum of distances* (or equivalently, the
smallest

*average distance*). Because of this property, it
is also known as the

*point of minimum aggregate travel*.
Unfortunately, there is no direct

closed-form formula for the geometric median; it
is typically computed using

iterative
methods.

## Determination

In practical computation, decisions are also made on the
granularity (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

[124753], 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 , 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", essentially located in Afghanistan, with an average distance of to all humans [124754]. 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.
### Bangladesh

The centre
of population for Bangladesh is close to Dhaka.
### Canada

In 1993,
the mean population centre of Canada was found to
be in the Township of Laxton,
Digby and Longford, Victoria County, now part of the city of
Kawartha
Lakes, Ontario.
### Finland

In
Finland, the point
of minimum aggregate travel is located in the municipality of
Hauho. 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.

### Germany

In
Germany, the centroid of the population is located in Spangenberg, Hesse close to
Kassel.
### Great Britain

The
centre 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.
### Japan

The
centroid 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.
More
recently, the only large regions in Japan with significant
population growth have been in Greater
Nagoya and Greater
Tokyo.
### Sweden

The
demographical center of
Sweden (using the median center definition) is Hjortkvarn in Hallsberg
municipality, Ã–rebro
county. Between the 1989 and 2007 census the point moved a
few kilometres to the south, due to a decreasing population in
northern Sweden and immigration to the south.

### Thailand

For
Thailand, the center of population lies in the central
plains area northwest of Bangkok.
### USA

The

mean center
of United States population (using the centroid definition) has
been calculated for each

U.S.
Census since 1790.

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 east-northeast of the new capital.
Over the last two centuries, the mean center of United States
population has progressed westward and, since 1930, southwesterly,
reflecting population drift.

## Sources

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

## References

## External links