Population growth

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^[16] and increases in agricultural productivity.^[17][18]

Haber process

Due to its dramatic impact on the human ability to grow food, the Haber process, named after one of its inventors, the German chemist Fritz Haber, 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.^[19]

Thomas McKeown hypotheses

Some of the reasons for the "Modern Rise of Population"^[20] 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,^[21][22]
2. The decline of mortality could largely be attributed to rising standards of living, whereby McKeown put most emphasis on improved nutritional status,
3. McKeown questioned the effectiveness of public health measures, including sanitary reforms, vaccination and quarantine,^[23]
4. The “McKeown thesis" states that curative medicine measures played little role in mortality decline, not only prior to the mid-20th century^[21] but also until well into the 20th century.^[24]

Although the McKeown thesis has been heavily disputed, recent studies have confirmed the value of his ideas.^[25] 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".^[26]

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:

${\displaystyle Population\ growth\ rate={\frac {P(t_{2})-P(t_{1})}{P(t_{1})(t_{2}-t_{1})}}}$

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.^[27]

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.^[28] In the world human population, growth may be said to have been following a linear trend throughout the last few decades.^[10]

Logistic equation

The growth of a population can often be modelled by the logistic equation^[29]

${\displaystyle {\frac {dP}{dt}}=rP\left(1-{\frac {P}{K}}\right),}$

where

• ${\displaystyle P(t)}$ = the population after time t;
• ${\displaystyle t}$ = time a population grows;
• ${\displaystyle r}$ = the relative growth rate coefficient;
• ${\displaystyle K}$ = the carrying capacity of the population; defined by ecologists as the maximum population size that a particular environment can sustain.^[28]

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

${\displaystyle P(t)={\frac {K}{1+Ae^{-rt}}}}$ ,

where ${\displaystyle A={\frac {K-P_{0}}{P_{0}}}}$ and ${\displaystyle P_{0}}$ is the initial population at time 0.

The world population growth rate peaked in 1963 at 2.2% per year and subsequently declined.^[10] In 2017, the estimated annual growth rate was 1.1%.^[30] The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.86%, 0.78%, and 1.08% respectively.^[31] 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.^[32]

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.^[30] Generally, developed nations have seen a decline in their growth rates in recent decades, though annual 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.^[33]

In some countries the population is declining, 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 experience population decline.^[34] Japan's population began decreasing in 2005.^[35]

The United Nations Population Division projects world population to reach 11.2 billion by the end of the 21st century. The Institute for Health Metrics and Evaluation projects that the global population will peak in 2064 at 9.73 billion and decline to 8.89 billion in 2100.^[11] A 2014 study in Science concludes that the global population will reach 11 billion by 2100, with a 70% chance of continued growth into the 22nd century.^[36][37] The German Foundation for World Population reported in December 2019 that the global human population grows by 2.6 people every second, and could reach 8 billion by 2023.^[38][39]

According to United Nations population statistics, the world population grew by 30%, or 1.6 billion humans, between 1990 and 2010.^[40] 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 (271%).^[40]

Growth rates of the world's most populous countries

Rank	Country	Population			Annual Growth (%)
		1990	2010	2020 (est.)[41]	1990–2010	2010–2020
	World	5,306,425,000	6,895,889,000	7,503,828,180	1.3%	0.8%
1	China	1,139,060,000	1,341,335,000	1,384,688,986	0.8%	0.3%
2	India	873,785,000	1,224,614,000	1,333,000,000	1.7%	0.9%
3	United States	253,339,000	310,384,000	329,256,465	1.0%	0.6%
4	Indonesia	184,346,000	239,871,000	262,787,403	1.3%	0.9%
5	Brazil	149,650,000	194,946,000	208,846,892	1.3%	0.7%
6	Pakistan	111,845,000	173,593,000	207,862,518	2.2%	1.8%
7	Nigeria	97,552,000	158,423,000	203,452,505	2.5%	2.5%
8	Bangladesh	105,256,000	148,692,000	159,453,001	1.7%	0.7%
9	Russia	148,244,000	142,958,000	142,122,776	-0.2%	−0.1%
10	Japan	122,251,000	128,057,000	126,168,156	0.2%	−0.1%

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,^[42] further straining its resources. Vietnam, Mexico, Nigeria, Egypt, Ethiopia, and the DRC are witnessing a similar growth in population.

The following table gives some example countries or territories:

Country/territory	Population in					Life expectancy in years (2008)	Total population growth from 1960s to 2007–2011
	1967	1990	1994	2002	2008
Eritrea*	N/A*	N/A*	3,437,000[43]	4,298,269	5,673,520[44]	61[45]	2,236,520
Ethiopia*	23,457,000*[46]	50,974,000* [47]	54,939,000[43]	67,673,031(2003)	79,221,000[48]	55[45]	55,764,000
Sudan	14,355,000†[46]	25,204,000† [47]	27,361,000†[43]	38,114,160 (2003)†	42,272,000†[44]	50†[45]	27,917,000
Chad	3,410,000[46]	5,679,000[47]	6,183,000[43]	9,253,493(2003)	10,329,208 (2009)[42]	47[45]	6,919,205
Niger	3,546,000[46]	7,732,000[47]	8,846,000[43]	10,790,352 (2001)	15,306,252 (2009)[49]	44[45]	11,760,252
Nigeria	61,450,000[46]	88,500,000[47]	108,467,000[43]	129,934,911	158,259,000[44]	47[45]	96,809,000
Mali	4,745,000[46]	8,156,000[47]	10,462,000[43]	11,340,480	14,517,176(2010)[50]	50[45]	9,772,176
Mauritania	1,050,000[46]	2,025,000 [47]	2,211,000[43]	2,667,859 (2003)	3,291,000 (2009)[42]	54[45]	2,241,000
Senegal	3,607,000[46]	7,327,000[47]	8,102,000[43]	9,967,215	13,711,597 (2009)[51]	57[45]	10,104,597
Gambia	343,000[46]	861,000[47]	1,081,000[43]	1,367,124 (2000)	1,705,000[44]	55[45]	1,362,000
Algeria	11,833,126 [46]	25,012,000[47]	27,325,000 [43]	32,818,500 (2003)	34,895,000[48][52]	74[45]	23,061,874
The DRC/Zaire	16,353,000[46]	35,562,000[47]	42,552,000[43]	55,225,478 (2003)	70,916,439 [48][53]	54[45]	54,563,439
Egypt	30,083,419 [46]	53,153,000[47]	58,326,000[43]	70,712,345 (2003)	79,089,650 [48][54]	72[45]	49,006,231
Réunion (overseas region of France)	418,000[46]	N/A[47]	N/A[43]	720,934 (2003)	827,000 (2009) [44]	N/A[45]	409,000
Falkland Islands (British Overseas Territory)	2,500[46]	N/A[47]	N/A[43]	2,967 (2003)	3,140(2010)[55]	N/A[45]	640
Chile	8,935,500[46]	13,173,000[47]	13,994,000[43]	15,116,435	17,224,200 (2011)	77[45]	8,288,700
Colombia	19,191,000[46]	32,987,000[47]	34,520,000[43]	41,088,227	45,925,397 (2010)[56]	73[45]	26,734,397
Brazil	85,655,000[46]	150,368,000[47]	153,725,000[43]	174,468,575 (2000)	190,732,694 (2010) [57]	72[45]	105,077,694
Mexico	45,671,000[46]	86,154,000[47]	93,008,000[43]	103,400,165 (2000)	112,322,757 (2010)[58]	76[45]	66,651,757
Fiji	476,727 (1966)[46]	765,000[47]	771,000[43]	844,330 (2001)	849,000[52] (2010)	70[45]	372,273
Nauru	6,050 [46]	10,000[47]	N/A[43]	12,329	9,322 (2011)[59]	N/A[45]	3,272
Jamaica	1,876,000[46]	2,420,000[47]	2,429,000[43]	2,695,867 (2003)	2,847,232[60](2010)	74[45]	971,232
Australia	11,540,764 [46]	17,086,000[47]	17,843,000[43]	19,546,792 (2003)	26,817,714[61] (2010)	82[45]	10,066,508
Albania	1,965,500 (1964)[46]	3,250,000[47]	3,414,000[43]	3,510,484	2,986,952 (July 2010 est.)[42][62]	78[45]	1,021,452
Poland	31,944,000[46]	38,180,000[47]	38,554,000[43]	38,626,349 (2001)	38,192,000 (2010)[63]	75[45]	6,248,000
Hungary	10,212,000[46]	10,553,000[47]	10,261,000[43]	10,106,017	9,979,000 (2010)[64]	73[45]	-142,000
Bulgaria	8,226,564 (1965)[46]	8,980,000[47]	8,443,000[43]	7,707,495(2000)	7,351,234 (2011)[65]	73[45]	-875,330
United Kingdom	55,068,000 (1966)[46]	57,411,000[47]	58,091,000[43]	58,789,194	62,008,048 (2010)[66]	79[45]	7,020,048
Ireland	2,884,002 (1966)[46]	3,503,000[47]	3,571,000[43]	3,840,838 (2000)	4,470,700[67] (2010)	78[45]	1,586,698
People's Republic of China	720,000,000[46]	1,139,060,000[47]	1,208,841,000[43]	1,286,975,468 (2004)	1,339,724,852 (2010)[68]	73[45]	619,724,852
Japan‡	98,274,961 (1965)[46]	123,537,000[47]	124,961,000[43]	127,333,002	127,420,000 (2010)[69]	82[45]	28,123,865
India#	511,115,000[46]	843,931,000[47]	918,570,000[43]	1,028,610,328 (2001)	1,210,193,422 (2011)[70]	69[45]	699,078,422
Singapore	1,956,000 (1967)[46]	3,003,000 (1990) [47]	2,930,000 (1994)[43]	4,452,732 (2002)	5,076,700 (2010)[71]	82 (2008)[45]	3,120,700
Monaco	24,000 (1967)[46]	29,000 (1990) [47]	N/A (1994)[43]	31,842 (2000)	35,586[72] (2010)	(2008)[45]	11,586
Greece	8,716,000 (1967)[46]	10,123,000 (1990) [47]	10,426,000 (1994)[43]	10,964,020 (2001)[73]	11,305,118 (2011)[74]	N/A (2008)[45]	2,589,118
Faroe Islands (Danish dependency)	38,000 (1967)[46]	N/A (1990) [47]	N/A (1994)[43]	46,345 (2000)	48,917 (2010) [75]	N/A (2008)[45]	18,917
Liechtenstein	20,000 (1967)[46]	29,000 (1990) [47]	N/A (1994)[43]	33,307 (2000)	35,789 (2009)[76]	(2008)[45]	15,789
South Korea	29,207,856 (1966)[46]	42,793,000 (1990) [47]	44,453,000 (1994)[43]	48,324,000 (2003)	48,875,000 (2010) [77]	(2008)[45]	19,667,144
North Korea	12,700,000 (1967)[46]	21,773,000 (1990) [47]	23,483,000 (1994)[43]	22,224,195 (2002)	24,051,218 (2010)[78]	(2008)[45]	11,351,218
Brunei	107,200 (1967)[46]	266,000 (1990) [47]	280,000 (1994)[43]	332,844 (2001)	401,890 (2011)[79]	76 (2008)[45]	306,609
Malaysia	10,671,000 (1967)[46]	17,861,000 (1990) [47]	19,489,000 (1994)[43]	21,793,293 (2002)	27,565,821 (2010)[80]	(2008)[45]	16,894,821
Thailand	32,680,000 (1967)[46]	57,196,000 (1990) [47]	59,396,000 (1994)[43]	60,606,947 (2000)[81]	63,878,267 (2011)[82]	(2008)[45]	31,198,267
Lebanon	2,520,000 (1967)[46]	2,701,000 (1990) [47]	2,915,000 (1994)[43]	3,727,703[83] (2003)	4,224,000[44] (2009)	- (2008)[45]
Syria	5,600,000 (1967)[46]	12,116,000 (1990) [47]	13,844,000 (1994)[43]	17,585,540 (2003)	22,457,763 (2011)[84]	-(2008)[45]
Bahrain	182,00 (1967)[46]	503,000 (1990) [47]	549,000 (1994)[43]	667,238 (2003)	1,234,596[85] (2010)	75 (2008)[45]
Sri Lanka	11,741,000 (1967)[46]	16,993,000 (1990) [47]	17,685,000 (1994)[43]	19,607,519 (2002)	20,238,000[52] (2009)	- (2008)[45]
Switzerland	6,050,000 (1967)[46]	6.712,000 (1990) [47]	6,994,000 (1994)[43]	7,261,200 (2002)	7,866,500[86] (2010)	- (2008)[45]
Luxembourg	335,000 (1967)[46]	381,000 (1990) [47]	401,000 (1994)[43]	439,539 (2001)	511,840 (2011)[87]	- (2008)[45]
Romania	19,105,056 (1966)[46]	23,200,000 (1990)[47]	22,736,000 (1994)[43]	21,680,974 (2002)	21,466,174[88] (2011)	- (2008)[45]
Niue (associated state of New Zealand)	1,900 (1966)[46]	N/A (1990)[47]	N/A (1994)[43]	2,134 (2002)	1,398 (2009)[89]	N/A (2008)[45]	-502
Tokelau (New Zealand territory)	5,194 (1966)[46]	N/A (1990)[47]	N/A (1994)[43]	1,445 (2001)	1,416 (2009)	N/A (2008)[45]	-3,778
Jamaica	1,876,000 (1967)[46]	2,420,000 (1990) [47]	2,429,000 (1994)[43]	2,695,867 (2003)	2,847,232[60] (2010)	74 (2008)[45]	971,232
Argentina	32,031,000 (1967)[46]	32,322,000 (1990)[47]	34,180,000 (1994)[43]	37,812,817 (2002)	40,091,359 (2010)	74 (2008)[45]	8,060,359
France	49,890,660 (1967)[46]	56,440,000 (1990)[47]	57,747,000 (1994)[43]	59,551,000 (2001)	63,136,180 (2011)[90]	81 (2008)[45]
Italy	52,334,000 (1967)[46]	57,662,000 (1990)[47]	57,193,000 (1994)[43]	56,995,744 (2002)	60,605,053[91] (2011)	80 (2008)[45]
Mauritius	774,000 (1967)[46]	1,075,000 (1990)[47]	1,104,000 (1994)[43]	1,179,137 (2000)	1,288,000 (2009)[52]	75 (2008)[45]	514,000
Guatemala	4,717,000 (1967)[46]	9,197,000 (1990)[47]	10,322,000 (1994)[43]	12,974,361 (2000)	13,276,517 (2009)	70 (2008)[45]	8,559,517
Cuba	8,033,000 (1967)[46]	10,609,000 (1990)[47]	10,960,000 (1994)[43]	11,177,743 (2002)	11,239,363 (2009)[92]	77 (2008)[45]
Barbados	246,000 (1967)[46]	255,000 (1990) [47]	261,000 (1994)[43]	250,012 (2001)	284,589 (2010)[42]	73 (2008)[45]	18,589
Samoa	131,377 (1967)[46]	164,000 (1990) [47]	164,000 (1994)[43]	178,173 (2003)	179,000 (2009)[44]	N/A (2008)[45]
Sweden	7,765,981 (1967)[46]	8,559,000 (1990) [47]	8,794,000 (1994)[43]	8,920,705 (2002)	9,354,462 (2009)	81 (2008)[45]
Finland	4,664,000 (1967)[46]	4,986,000 (1990) [47]	5,095,000 (1994)[43]	5,175,783 (2002)	5,374,781 (2010)	N/A (2008)[45]
Portugal	9,440,000 (1967)[46]	10,525,000 (1990)[47]	9,830,000 (1994)[43]	10,355,824 (2001)	10,647,763[93] (2011)	N/A (2008)[45]
Austria	7,323,981 (1967)[46]	7,712,000 (1990) [47]	8,031,000 (1994)[43]	8,032,926 (2001)	8,404,252 (2011)	N/A (2008)[45]
Libya	1,738,000 (1967)[46]	4,545,000 (1990)[47]	5,225,000(1994)[43]	5,499,074 (2002)	6,420,000 (2009)[44]	77 (2008)[45]
Peru	12,385,000 (1967)[46]	21,550,000 (1990)[47]	23,080,000(1994)[43]	27,949,639 (2002)	29,496,000 (2010)	70 (2008)[45]
Guinea Bissau	528,000 (1967)[46]	965,000 (1990) [47]	1,050,000 (1994)[43]	1,345,479 (2002)	1,647,000[44] (2009)	48 (2008)[45]
Angola	5,203,066 (1967)[46]	10,020,000 (1990)[47]	10,674,000 (1994)[43]	10,766,500 (2003)	18,498,000[52][94] (2009)	38 (2008)[45]
Equatorial Guinea	277,000 (1967)[46]	348,000 (1990)[47]	389,000 (1994)[43]	474,214 (2000)	676,000 (2009)[52]	61 (2008)[45]
Benin	2,505,000 (1967)[46]	4,736,000 (1990)[47]	5,246,000 (1994)[43]	8,500,500 (2002)	8,791,832 (2009)	59 (2008)[45]
Laos	2,770,000 (1967)[46]	4,139,000 (1990)[47]	4,742,000 (1994)[43]	5,635,967 (2002)	6,800,000[95] (2011)	56 (2008)[45]
Nepal	10,500,000 (1967)[46]	18,961,000 (1990)[47]	21,360,000 (1994)[43]	25,284,463 (2002)	29,331,000[52] (2009)	- (2008)[45]
Iran	25,781,090 (1966)[46]	54,608,000 (1990)[47]	59,778,000 (1994)[43]	66,622,704 (2002)	75,330,000 (2010)[96]	71 (2008)[45]	49,548,910
Canada	20,014,880 (1966)[46]	26,603,000 (1990)[47]	29,248,000(1994)[43]	31,081,900 (2001)	32,623,490 (2011)[97]	81 (2008)[45]
United States	199,118,000 (1967)[46]	249,995,000 (1990)[47]	260,650,00(1994)[43]	281,421,906 (2000)	308,745,538 (2010)[98]	78 (2008)[45]
Uganda	7,931,000 (1967)[46]	18,795,000 (1990)[47]	20,621,000 (1994)[43]	24,227,297 (2002)	32,369,558 (2009)	52 (2008)[45]

Notes

* Eritrea left Ethiopia in 1991.

† Split into the nations of Sudan and South Sudan during 2011.

‡ Japan and the Ryukyu Islands merged in 1972.

# India and Sikkim merged in 1975.

• List of countries by population growth rate
• Demographic history
• Demographic transition
• Density dependence
• Ecological overshoot
• Epidemiological transition
• Human population planning
• Irruptive growth
• Overshoot (population)
• Population decline
• Population density
• World population
• Estimates of historical world population
• Zero population growth

External videos
Food Production and Population Growth - Daniel Quinn

• "World Population Prospects". Website of the United Nations Population Division. Archived from the original on 11 July 2017.
• "Food Production and Population Growth". Daniel Quinn, Alan D. Thornhill, PhD. Ecofuture. Population and Sustainability Media, Non-fiction.
• "Probabilistic Population Projections, 2nd Revision". Website of the United Nations Population Division. Archived from the original on 4 October 2013.
• "Population Growth and the Food Supply". Population Institute of Canada.
• "World population growth and trends 1950-2050". US Census. Archived from the original on 7 July 2010.
• "Feeding the Ten Billion-Plants and Population Growth". PGR Newsletter FAO-Bioversity L.T. Evans. 2000. Cambridge University Press. ISBN 0-521-64685-5. Published in Issue No. 125, page 39 to 40 - (5802) characters