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Population growth is the increase in the number of individuals in a population. Global human population growth amounts to around 83 million annually,[2] or 1.1% per year. The global population has grown from 1 billion in 1800 to 7.8 billion[3] in 2020. It is expected to keep growing, and estimates have put the total population at 8.6 billion by mid-2030, 9.8 billion by mid-2050 and 11.2 billion by 2100.[4] Many nations with rapid population growth have low standards of living, whereas many nations with low rates of population growth have high standards of living.[5]

Population[6]
Years passed Year Billion
1800 1
127 1927 2
33 1960 3
14 1974 4
13 1987 5
12 1999 6
12 2011 7
12 2023* 8
14 2037* 9
18 2055* 10
33 2088* 11
*World Population Prospects 2017
(United Nations Population Division)

History

World human population estimates from 1800 to 2100, with estimated range of future population after 2020 based on "high" and "low" scenarios. Data from the United Nations projections in 2019.

World population has been rising continuously since the end of the Black Death, around the year 1350.[7] Population began growing rapidly in the Western world during the industrial revolution. The most significant increase in the world's population has been since the 1950s, mainly due to medical advancements[8] and increases in agricultural productivity.[9]

Haber process

Due to its dramatic impact on the human ability to grow food, the Haber process served as the "detonator of the population explosion", enabling the global population to increase from 1.6 billion in 1900 to 7.7 billion by November 2019.[10]

Thomas McKeown hypotheses

Some of the reasons for the "Modern Rise of Population"[11] were particularly investigated by the British health scientist Thomas McKeown (1912-1988). In his publications, McKeown challenged four theories about the population growth:

  1. McKeown stated that the growth in Western population, particularly surging in the 19th century, was not so much caused by an i

    World population has been rising continuously since the end of the Black Death, around the year 1350.[7] Population began growing rapidly in the Western world during the industrial revolution. The most significant increase in the world's population has been since the 1950s, mainly due to medical advancements[8] and increases in agricultural productivity.[9]

    Haber process

    Due to its dramatic impact on the human ability to grow food, the Haber process served as the "detonator of the population explosion", enabling the global population to increase from 1.6 billion in 1900 to 7.7 billion by November 2019.[10]

    Thomas McKeown hypotheses

    Some of the reasons for the "Modern Rise of Population"[11] were particularly investigated by the British health scientist Thomas McKeown (1912-1988). In his publications, McKeown challenged four theories about the population growth:

    1. McKeown stated that the growth in Western population, particularly surging in the 19th century, was not so much caused by an increase in fertility, but largely by a decline of mortality particularly of childhood mortality followed by infant mortality,[12][13]
    2. The decline of mortality could largely be attributed to rising standards of living, whereby McKeown put most emphasis on improved nutritional status,
    3. His most controversial idea, at least his most disputed idea, was that he questioned the effectiveness of public health measures, including sanitary reforms, vaccination and quarantine,[14]
    4. The sometime fierce disputes that his publication provoked around the "McKeown thesis", have overshadowed his more important and largely unchallenged argument that curative medicine measures played little role in mortality decline, not only prior to the mid-20th century[12] but also until well into the 20th century.[15]

    Although the McKeown thesis has been heavily disputed, recent studies have confirmed the value of his ideas.[16] His work is pivotal for present day thinking about population growth, birth control, public health and medical care. McKeown had a major influence on many population researchers, such as health economists and Nobel prize winners Robert W. Fogel (1993) and Angus Deaton (2015). The latter considered McKeown as "the founder of social medicine".[17]

    Population growth rate

    External video
    video iconHaber process served as the "detonator of the population explosion", enabling the global population to increase from 1.6 billion in 1900 to 7.7 billion by November 2019.[10]

    Thomas McKeown hypotheses

    Some of the reasons for the "Modern Rise of Population"[11] were particularly investigated by th

    Some of the reasons for the "Modern Rise of Population"[11] were particularly investigated by the British health scientist Thomas McKeown (1912-1988). In his publications, McKeown challenged four theories about the population growth:

    1. McKeown stated that the growth in Western population, particularly surging in the 19th century, was not so much caused by an increase in fertility, but largely by a decline of mortality particularly of childhood mortality followed by [16] His work is pivotal for present day thinking about population growth, birth control, public health and medical care. McKeown had a major influence on many population researchers, such as health economists and Nobel prize winners Robert W. Fogel (1993) and Angus Deaton (2015). The latter considered McKeown as "the founder of social medicine".[17]

      Population growth rate

      External video
      video icon Human Population Through Time

      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

      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:

    2. = t

      As it is a separable differential equation, the population may be solved explicitly, producing a logistic function:

      ,

      where and

      where and is the initial population at time 0.

      Human population growth rate

      External video
      video icon How Earth's Population Exploded