In biology, population growth is the increase in the number of individuals in a population. The population growth rate is the rate at which the number of individuals in a population increases in a given time period as a fraction of the initial population.
Global human population growth amounts to around 75 million annually, or 1.1% per year. The global population has grown from 1 billion in 1800 to 7 billion in 2012. It is expected to keep growing, where estimates have put the total population at 8.4 billion by mid-2030, and 9.6 billion by mid-2050.[1]
The "population growth rate" is the rate at which the number of individuals in a population increases in a given time period, expressed as a fraction of the initial population. Specifically, population growth rate refers to the change in population over a unit time period, often 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, valid for a sufficiently small time interval:
A positive growth rate indicates that the population is increasing, while a negative growth rate indicates that the population is decreasing. A growth ratio of zero indicates that there were the same number of individuals at the beginning and end of the period—a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times.[3]
A related measure is the net reproduction rate. In the absence of migration, a net reproduction rate of more than 1 indicates that the population of females is increasing, while a net reproduction rate less than one (sub-replacement fertility) indicates that the population of females is decreasing.
Estimates of population evolution in different continents between 1950 and 2050, according to the United Nations. The vertical axis is logarithmic and is in millions of people.
Growth rate of world population (1950–2050).
Globally, the growth rate of the human population has been declining since peaking in 1962 and 1963 at 2.2% per annum. In 2009, the estimated annual growth rate was 1.1%.[4] The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.89%, 0.79%, and 1.096% respectively.[5] The last 100 years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity[6] made possible by the Green Revolution.[7][8][9]
The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050, at which time the population will have increased to about 9.2 billion.[4] Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America.[10]
Some countries experience negative population growth, especially in Eastern Europe mainly due to low fertility rates, high death rates and emigration. In Southern Africa, growth is slowing due to the high number of AIDS-related deaths. Some Western Europe countries might also encounter negative population growth.[11]Japan's population began decreasing in 2005.[12] The United Nations Population Division expects world population to peak at over 10 billion at the end of the 21st century but Sanjeev Sanyal has argued that global fertility will fall below replacement rates in the 2020s and that world population will peak below 9 billion by 2050 followed by a long decline.[13]
According to United Nations population statistics, the world population grew by 30%, or 1.6 billion people, between 1990 and 2010.[14] In number of people the increase was highest in India (350 million) and China (196 million). Population growth was among highest in the United Arab Emirates (315%) and Qatar (271%).[14]
Growth rates of the world's most populous countries
The majority of world population growth today is occurring in less developed countries.
According to UN's 2010 revision to its population projections, world population will peak at 10.1bn in 2100 compared to 7bn in 2011.[46] A 2014 paper by demographers from several universities and the United Nations Population Division forecast that the world's population will reach about 10.9 billion in 2100 and continue growing thereafter.[47] However, some experts dispute the UN's forecast and have argued that birthrates will fall below replacement rate in the 2020s. According to these forecasters, population growth will be only sustained till the 2040s by rising longevity but will peak below 9bn by 2050.[48]
^ abDepartment of Economic and Social Affairs Population Division (2009). "World Population Prospects, Table A.1"(PDF). 2008 revision. United Nations. Retrieved 2009-03-12.
^ abcDepartment of Economic and Social Affairs Population Division (2010). "World Population Prospects, Table A.1"(PDF). 2008 revision. United Nations. Retrieved 2009-03-12.[dead link]Cite error: Invalid <ref> tag; name "unpop" defined multiple times with different content (see the help page).
^"Population clock". Australian Bureau of Statistics website. Commonwealth of Australia. Retrieved 12 April 2011. The population estimate shown is automatically calculated daily at 00:00 UTC and is based on data obtained from the population clock on the date shown in the citation.