is the increase in the number of individuals in a population
. Global human population growth amounts to around 83 million annually,
or 1.1% per year. The global population
has grown from 1 billion in 1800 to 7.9 billion
in 2020. The UN projected population 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.
However, some academics outside the UN have increasingly developed human population models
that account for additional downward pressures on population growth; in such a scenario population would peak before 2100.
Absolute increase in global human population per year
World human population has been growing since the end of the Black Death
, around the year 1350.
A mix of technological advancement that improved agricultural productivity
and sanitation and medical advancement that reduced mortality have caused a exponential population growth. In some geographies, this has slowed through the process called the demographic transition
, where many nations with high standards of living have seen a significant slowing of population growth. This is in direct contrast with less developed contexts, where population growth is still happening.
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
Thomas McKeown hypotheses
Some of the reasons for the "Modern Rise of Population"
were particularly investigated by the British health scientist Thomas McKeown
(1912-1988). In his publications, McKeown challenged four theories about the population growth:
- 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,
- The decline of mortality could largely be attributed to rising standards of living, whereby McKeown put most emphasis on improved nutritional status,
- 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,
- 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 but also until well into the 20th century.
Although the McKeown thesis has been heavily disputed, recent studies have confirmed the value of his ideas.
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
Population growth rate
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.
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.
Most populations do not grow exponentially, rather they follow a logistic model
. Once the population has reached its carrying capacity
, it will stabilize and the exponential curve will level off towards the carrying capacity, which is usually when a population has depleted most its natural resources
The logistic growth of a population.
- = the population after time t;
- = time a population grows;
- = the relative growth rate coefficient;
- = the carrying capacity of the population; defined by ecologists as the maximum population size that a particular environment can sustain.
As it is a separable differential equation, the population may be solved explicitly, producing a logistic function
is the initial population at time 0.
Human population growth rate
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.
World population growth rates between 1950 and 2050
In 2017, the estimated annual growth rate was 1.1%.
The CIA World Factbook
gives the world annual birthrate, mortality rate, and growth rate as 1.86%, 0.78%, and 1.08% respectively.
The last 100 years have seen a massive fourfold increase in the population, due to medical advances
, lower mortality rates, and an increase in agricultural productivity made possible by the Green Revolution
The annual increase in the number of living humans peaked at 88.0 million in 1989, then slowly declined to 73.9 million in 2003, after which it rose again to 75.2 million in 2006. In 2017, the human population increased by 83 million.
Generally, developed nations have seen a decline in their growth rates in recent decades, though annual growth rates remain above 2% in poverty-stricken countries of the Middle East
and Sub-Saharan Africa
, and also in South Asia
, Southeast Asia
, and Latin America
Growth by country
According to United Nations
population statistics, the world population grew by 30%, or 1.6 billion humans, between 1990 and 2010.
In number of people the increase was highest in India (350 million) and China (196 million). Population growth rate was among highest in the United Arab Emirates
(315%) and Qatar
Growth rates of the world's most populous countries
Many of the world's countries, including many in Sub-Saharan Africa
, the Middle East
, South Asia
and South East Asia
, have seen a sharp rise in population since the end of the Cold War
. The fear is that high population numbers are putting further strain on natural resources, food supplies, fuel supplies, employment, housing, etc. in some of the less fortunate countries. For example, the population of Chad
has ultimately grown from 6,279,921 in 1993 to 10,329,208 in 2009,
further straining its resources. Vietnam
, and the DRC
are witnessing a similar growth in population.
The following table gives some example countries:
* Eritrea left Ethiopia in 1991.
† Split into the nations of Sudan and South Sudan
‡ Japan and the Ryukyu Islands merged in 1972.
# India and Sikkim merged in 1975.
Nilkhet Mor in Dhaka by Nahid 02. Bangladesh is one of the most densely populated countries in the world.
World population growth 1700–2100
Population projections are attempts to show how the human population living today will change in the future.
These projections are an important input to forecasts
of the population's impact on this planet and humanity's future well-being.
Models of population growth take trends in human development, and apply projections into the future. These models use trend-based-assumptions about how populations will respond to economic, social and technological forces to understand how they will effect fertility
and mortality, and thus population growth.
The 2019 forecast from the United Nation's Population Division (made before the COVID-19 pandemic
) shows that world population growth peaked at 2.1% per year in 1968, has since dropped to 1.1%, and could drop even further to 0.1% by 2100, a growth rate not seen since pre-industrial revolution days.
Based on this, the UN Population Division expects world population, currently (2020) at 7.8 billion, to level out at or soon after the end of the 21st
Century at 10.9 billion (the median line),
assuming a continuing decrease in the global average fertility rate
from 2.5 births per woman during the 2015–2020 period to 1.9 in 2095–2100, according to the medium-variant projection.
About two thirds of the predicted growth in population between 2020 and 2050 will take place in Africa.
World population prospects, 2019
Because of population momentum
the global population could continue to grow, although at a steadily slower rate, for the remainder of this century, but the main driver of long-term future population growth will be the evolution of the global average fertility rate.
However, estimates outside of the United Nations have put forward alternative models based on additional downward pressure on fertility (such as successful implementation of education and family planning goals in the Sustainable Development Goals
) -- which could result in peak population mid-21st century rather than later.
Estimated size of human population from 10,000 BCE
to 2000 CE.
The majority of world population growth today is occurring in less developed countries.
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