# Population density

Population density (in agriculture: standing stock and standing crop) is a measurement of population per unit area or unit volume; it is a quantity of type number density. It is frequently applied to living organisms, and most of the time to humans. It is a key geographical term.[1] In simple terms population density refers to the number of people living in an area per kilometer square.

Population density (people per km2) by country, 2006
Population density (people per km2) map of the world in 1994. In relation to the equator it is seen that the vast majority of the human population lives in the Northern Hemisphere, which is logical, as 85% of the Earth's land area is there.
Population density (people per km2) map of the world in 1994
Deserts around the world. Compare with maps above. See also this image for location of densely populated areas (cities) in various vegetation zones.

## Biological population densities

Population density is population divided by total land area or water volume, as appropriate.[1]

Low densities may cause an extinction vortex and lead to further reduced fertility. This is called the Allee effect after the scientist who identified it. Examples of the causes in low population densities include:[2]

• Increased problems with locating sexual mates
• Increased inbreeding
Monaco in Southern Europe, currently holds the record for being the most densely populated nation in the world.
Mongolia is the least densely populated country in the world.
This population cartogram of the European Union (2007–2012) uses areas and colors to represent population.

For humans, population density is the number of people per unit of area, usually quoted per square kilometer or square mile (which may include or exclude, for example, areas of water or glaciers). Commonly this may be calculated for a county, city, country, another territory or the entire world.

The world's population is around 7,500,000,000[3] and Earth's total area (including land and water) is 510,000,000 square kilometers (197,000,000 sq. mi.).[4] Therefore, the worldwide human population density is around 7,500,000,000 ÷ 510,000,000 = 14.7 per km2 (38 per sq. mi). If only the Earth's land area of 150,000,000 km2 (58,000,000 sq. mi.) is taken into account, then human population density is 50 per km2 (129 per sq. mile). This includes all continental and island land area, including Antarctica. If Antarctica is also excluded, then population density rises to over 55 people per km2 (over 142 per sq. mile).[1] However, over half of the Earth's land mass consists of areas inhospitable to human habitation, such as deserts and high mountains, and population tends to cluster around seaports and fresh-water sources. Thus, this number by itself does not give any helpful measurement of human population density.

Several of the most densely populated territories in the world are city-states, microstates and dependencies.[5][6] These territories have a relatively small area and a high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation

The potential to maintain the agricultural aspects of deserts is extremely limited as there is not enough precipitation to support a sustainable land. The population in these areas are extremely low. Therefore, cities in the Middle East, such as Dubai, have been increasing in population and infrastructure growth at a fast pace.[7]

Cities with high population densities are, by some, considered to be overpopulated, though this will depend on factors like quality of housing and infrastructure and access to resources.[8] Most of the most densely populated cities are in Southeast Asia, though Cairo and Lagos in Africa also fall into this category.[9]

City population and especially area are, however, heavily dependent on the definition of "urban area" used: densities are almost invariably higher for the central city area than when suburban settlements and the intervening rural areas are included, as in the areas of agglomeration or metropolitan area, the latter sometimes including neighboring cities. For instance, Milwaukee has a greater population density when just the inner city is measured, and the surrounding suburbs excluded.[10]

In comparison, based on a world population of seven billion, the world's inhabitants, as a loose crowd taking up ten square feet (one square metre) per person (Jacobs Method), would occupy a space a little larger than Delaware's land area.

### Countries and dependent territories

With population under 10,000,000
Pos. Country (or dependent territory) Area (km2) Area (mi2) Population Density
(pop./km2)
Density
(pop./mi2)
1  Macau (China) 30.5 12 650,834 21,339 55,268
2  Monaco 2.02 0.78 37,550 18,589 48,145
3  Singapore 719.9 278 5,612,300 7,796 20,192
4  Hong Kong (China) 1,106.3 427 7,409,800 6,698 17,348
5  Gibraltar (UK)[11] 6.8 2.6 33,140 4,874 12,624
6  Bahrain 757 292 1,451,200 1,917 4,965
7   Vatican City 0.44 0.17 800 1,818 4,709
8  Malta 315 122 475,701 1,510 3,911
9  Maldives 298 115 378,114 1,269 3,287
10  Bermuda (UK) 52 20 63,779 1,227 3,178

The Gaza Strip (exclave of Palestine) has a population of 1.85 million and a population density of 5,046 pop/km.

With population above 10,000,000
Pos. Country (or dependent territory) Area (km2) Area (mi2) Population Density
(pop./km2)
Density
(pop./mi2)
12  Bangladesh 143,998 55,598 165,001,946 1,146 2,968
19  Taiwan 36,193 13,974 23,572,049 651 1,686
25  South Korea 100,210 38,691 51,635,256 515 1,334
27  Rwanda 26,338 10,169 12,001,136 456 1,181
31  Netherlands 41,526 16,033 17,271,819 416 1,077
33  Haiti 27,065 10,450 11,112,945 411 1,064
34  India 3,287,240 1,269,210 1,335,543,957 406 1,052
36  Burundi 27,816 10,740 10,681,186 384 995
38  Belgium 30,528 11,787 11,414,214 374 969
39  Philippines 300,000 115,831 106,302,840 354 917

### Other methods of measurement

Although arithmetic density is the most common way of measuring population density, several other methods have been developed to provide a more accurate measure of population density over a specific area.

• Arithmetic density: The total number of people / area of land (measured in square miles or square kilometers)
• Physiological density: The total population / area of arable land
• Agricultural density: The total rural population / area of arable land
• Residential density: The number of people living in an urban area / area of residential land
• Urban density: The number of people inhabiting an urban area / total area of urban land
• Ecological optimum: The density of population that can be supported by the natural resources

## References

1. ^ a b c Matt Rosenberg Population Density. Geography.about.com. March 2, 2011. Retrieved on December 10, 2011.
2. ^ Minimum viable population size. Eoearth.org (March 6, 2010). Retrieved on December 10, 2011.
3. ^ U.S. & World Population Clocks. Census.gov. Retrieved on December 10, 2011.
4. ^ World. CIA World Handbook
5. ^ Department of Economic and Social Affairs Population Division (2009). "World Population Prospects, Table A.1" (PDF). 2008 revision. United Nations. Retrieved March 12, 2009.
6. ^ The Monaco government uses a smaller surface area figure resulting in a population density of 18,078 per km2
7. ^ 1923-2009., Portnov, B. A. (Boris Adolʹfovich) Hare, A. Paul (Alexander Paul), (1999). Desert regions : population, migration, and environment. Springer. ISBN 3540657800. OCLC 41320143.
8. ^ Human Population. Global Issues. Retrieved on December 10, 2011.
9. ^ The largest cities in the world by land area, population and density. Citymayors.com. Retrieved on December 10, 2011.
10. ^ The Population of Milwaukee County. Wisconline.com. Retrieved on December 10, 2011.
11. ^ Territory claimed by Spain.