Population growth

From Wikipedia, the free encyclopedia

Image:Population curve.svg Population growth is change in population over time, and can be quantified as the change in the number of individuals in a population per unit time. The term population growth can technically refer to any species, but almost always refers to humans, and it is often used informally for the more specific demographic term population growth rate (see below), and is often used to refer specifically to the growth of the population of the world.

Simple models of population growth include the Malthusian Growth Model and the logistic model.

1 Population growth rate
2 Human population growth rate
3 References
4 See also
5 External links

[edit] Population growth rate

In demographics and ecology, Population growth rate (PGR) is the fractional rate at which the number of individuals in a population increases. Specifically, PGR ordinarily refers to the change in population over a specific time period expressed as a percentage of the number of individuals in the population at the beginning of that period. This can be written as the formula:

<math>\mathrm{Population\ Growth\ Rate} = {(\mathrm{Birth\ Rate} + \mathrm{Immigration}) - (\mathrm{Mortality\ Rate} + \mathrm{Emigration}) \over \mathrm{Population\ Size}}</math>

The crude death rate as defined above and applied to a whole population can give a misleading impression. For example, the number of deaths per 1000 people can be higher for developed nations than in less-developed countries, despite standards of health being better in developed countries.

[edit] Human population growth rate

Image:Population growth rate world.PNG

Globally, the growth rate of the human population has been steadily declining (ie. population is growing more slowly than in the recent past, see External Links), but growth remains high in the Middle East and Sub-Saharan Africa.<ref>Ron Nielsen, The little green handbook, Picador, New York (2006) ISBN 0-312-42581-4</ref> In some countries there is negative population growth (ie. net decrease in population over time), especially in Central and Eastern Europe (mainly due to low fertility rates) and Southern Africa (due to the high number of HIV-related deaths). Within the next decade, Japan and Western Europe are also expected to encounter negative population growth due to sub-replacement fertility rates. According to data from the CIA's World Factbook, the world human population currently increases by 203,800 every day.<ref>Current world population (ranked)</ref>

Population growth which exceeds the carrying capacity of an area or environment results in overpopulation. Conversely, such areas may be considered "underpopulated" if the population is not large enough to maintain an economic system (see population decline).