Projections of population growth

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World population estimates from 1800 to 2100, based on "high", "medium" and "low" United Nations projections in 2015 and UN historical estimates for pre-1950 data.

Projections of population growth established in 2015 predict that the human population will keep growing until at least 2050, reaching an estimated 8 billion people in 2024 and 9 billion by 2040, while the 7 billion milestone was reached in 2011.[1] As the demographic transition follows its course worldwide, the population will age significantly, with most countries outside Africa trending towards a rectangular age pyramid.[2]

According to the 2015 edition of the United Nations' World Population Prospects report, the world population is currently growing by approximately 83 million people each year.[3]:2 The growth rate keeps slowing, having decreased from 1.55% per year in 1995 to 1.25% in 2005 and 1.18% in 2015. The median estimate for future growth sees the world population reaching 9.7 billion in 2050 and 11.2 billion in 2100,[3]:2 assuming a continuing decrease in average fertility rate from 2.5 in 2015 to 2.25 in 2050 and 2.0 in 2100.[3]:10 With longevity trending towards uniform and stable values worldwide, the main driver of future population growth is the evolution of the fertility rate.[3]:8

While most scenarios still predict continued growth into the 22nd century, there is a roughly 23% chance that the total population could stabilize or begin to fall before 2100.[3]:3 Longer-term speculative scenarios over the next two centuries can predict anything between runaway growth to radical decline (36.4 billion or 2.3 billion people in 2300), with the median projection showing a slight decrease followed by a stabilization around 9 billion people.[4]:13

By 2050, the bulk of the world's population growth will take place in Africa: of the additional 2.4 billion people projected between 2015 and 2050, 1.3 billion will be added in Africa, 0.9 billion in Asia and only 0.2 billion in the rest of the world. Africa's share of global population is projected to grow from 16% in 2015 to 25% in 2050 and 39% by 2100, while the share of Asia will fall from 60% in 2015 to 54% in 2050 and 44% in 2100.[3]:3 The strong growth of the African population will happen regardless of the rate of decrease of fertility, because of the exceptional proportion of young people already living today. For example, the UN projects that the population of Nigeria will surpass that of the United States by 2050.[3]:4 The population of the more developed regions is slated to remain mostly unchanged, at 1.2 billion, as international migrations from high-growth regions compensate the fertility deficit of richer countries.[3]:11

Growth regions[edit]

A world map showing global variations in fertility rate per woman, according to the CIA World Factbook's 2015 data.

During 2005–2050, twelve countries are expected to account for half of the world's projected population increase: India, China, United States, Indonesia, Nigeria, Pakistan, Brazil, Democratic Republic of the Congo, Ethiopia, Philippines, Mexico and Egypt, listed according to the size of their contribution to population growth.

In 2010–2015, the average world fertility was 2.5 children per woman, about half the level in 1950–1955 (5 children per woman). In the medium variant, global fertility is projected to decline further to 2.25 children per woman in 2045–2050 and 2.0 in 2095–2100.[3]:10

Global life expectancy at birth, which is estimated to have risen from 46 years in 1950–1955 to 65 years in 2000–2005, is expected to keep rising to reach 75 years in 2045–2050. In the more developed regions, the projected increase is from 75 years today to 82 years by mid-century. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to be 66 years in 2045–2050. The population of 31 countries or areas, including Ukraine, Romania, Japan and most of the successor States of the former Soviet Union, is expected to be lower in 2050 than in 2005.

Projected migration to Western countries[edit]

According to the United Nations, during 2005–2050 the net number of international migrants to more developed regions is projected to be 98 million. Because deaths are projected to exceed births in the more developed regions by 73 million during 2005–2050, population growth in those regions will largely be due to international migration. In 2000–2005, net migration in 28 countries either prevented population decline or doubled at least the contribution of natural increase (births minus deaths) to population growth. These countries include Austria, Canada, Croatia, Denmark, Germany, Italy, Portugal, Qatar, Singapore, Spain, Sweden, the United Arab Emirates and the United Kingdom.[5]

By 2050 (Medium variant), India will have 1.660 billion people, China 1.425 billion, United States 440 million, Nigeria 391 million, Indonesia 327 million, Pakistan 308 million, Brazil 238.3 million, Bangladesh 201.8 million, Democratic Republic of Congo 195.3 million, Ethiopia 188.5 million, Mexico 164 million, Philippines 157.1 million, Egypt 142 million, Russia 133 million, Tanzania 129.4 million, Vietnam 112.8 million, Japan 107 million, Uganda 101 million, Turkey 96 million, Kenya 95.5 million, Iran 92.1 million, Sudan 81 million, Germany 78 million and the United Kingdom 75 million.

World population in 2050[edit]

Estimates of population levels in different continents between 1950 and 2050, according to the United Nations. The vertical axis is logarithmic and is in millions of people.

The median scenario of the UN 2015 world population prospects[3]:2 predicts the following populations per continent in 2050:

Walter Greiling projected in the 1950s that world population would reach a peak of about nine billion, in the 21st century, and then stop growing after a readjustment of the Third World and a sanitation of the tropics.[6] Recent extrapolations from available figures for population growth show that the population of Earth will stop increasing around 2070.[7]

In a 2004 long-term prospective report, the United Nations Population Division projected the world population to peak at 9.22 billion in 2075. After reaching this maximum, it would decline slightly and then resume a slow increase, reaching a level of 8.97 billion by 2300, about the same as the projected 2050 figure.[4]:1 However, with more recent data on hand, the same institution in 2015 predicted continued growth beyond 2100.[3]:2 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.[8]

Jørgen Randers, one of the authors of the seminal 1972 long-term simulations in The Limits to Growth, offered an alternative scenario in a 2012 book, arguing that traditional projections insufficiently take into account the downward impact of global urbanization on fertility. Randers' "most likely scenario" predicts a peak in the world population in the early 2040s at about 8.1 billion people, followed by decline.[9]

These projected growth patterns depend on assumptions about vital rates. Total fertility is assumed to continue to decline, at varying paces depending on circumstances in individual countries, to a below-replacement level of 1.85 children per woman by mid century. Countries already at this level or below, and other countries when they reach it, will eventually return to replacement over a period of a century and stay at replacement going forward. All countries are projected to have reached replacement fertility by 2175.

Some of the authors of the 2004 UN report say that life expectancy is assumed to rise slowly and continuously. The projections in the report assume this with no upper limit, though at a slowing pace depending on circumstances in individual countries. By 2100, the report assumes life expectancy to be from 66 to 97 years, and by 2300 from 87 to 106 years, depending on the country. Based on that assumption, they said that rising life expectancy will produce small but continuing population growth by the end of the projections, ranging from 0.03 to 0.07 percent annually.

However, based on recent research, many expect that life expectancy will leap ahead and indefinite human lifespans are not necessarily unfeasible.[10][11][12] This could significantly raise the estimates. In an essay within the U.N. report, Tim Dyson said,

"A rapid increase in life expectancy, which would raise the population pyramids, seems within reach, since it responds to an old and powerful demand for longevity."[4]

Most populous nations by 2030[edit]

The UN Population Division has calculated the future population of the world's countries, based on current demographic trends. The 2015 study projects the world population in 2030 to be 8.5 billion people, with the following estimates for the top 10 countries:[3]:18

2030 rank
(projected)
2015 rank Rank change Country 2030 population
(projected)
2015 population Population
change
1 2 +1 Increase  India (demographics) 1,527,658,000 1,311,051,000 +16.5%
2 1 −1 Decrease  China (demographics) 1,415,545,000 1,376,049,000 +2.9%
3 3 = Steady  United States (demographics) 355,765,000 321,774,000 +10.6%
4 4 = Steady  Indonesia (demographics) 295,482,000 257,564,000 +14.8%
5 7 +2 Increase  Nigeria (demographics) 262,599,000 182,202,000 +44.2%
6 6 = Steady  Pakistan (demographics) 244,916,000 188,925,000 +29.7%
7 5 −2 Decrease  Brazil (demographics) 228,663,000 207,848,000 +10.1%
8 8 = Steady  Bangladesh (demographics) 186,460,000 160,996,000 +15.9%
9 11 +2 Increase  Mexico (demographics) 148,133,000 127,017,000 +16.7%
10 9 −1 Decrease  Russia (demographics) 138,652,000 143,457,000 −3.3%
 World (demographics) 8,500,766,000 7,349,472,000 +15.7%

After 2050[edit]

Projections for after 2050 have usually assumed that fertility rates will have declined by then and the population will be stable or will decrease. However, a study in 2014 found that fertility rates in Africa have leveled off at around 4.6 instead of continuing to decline, and that consequently world population may be as high as 12 billion by 2100. Reasons for the continuing high fertility rate include better survival rates with respect to HIV, and lack of availability of contraception.[13][14] Another study on the other hand concludes that education of women will lead to low fertility rates even in Africa.[13] Evolutionary biology also suggests the demographic transition may reverse itself; in addition, recent evidence suggests birth rates may be rising in the 21st century in the developed world.[15]

Population projections of the 101 largest cities in the 21st century[edit]

Large urban areas are hubs of economic development and innovation, with larger cities underpinning regional economies and local and global sustainability initiatives. Currently, 757 million humans live in the 101 largest cities;[16] these cities are home to 11% of the world’s population.[16] By the end of the century, the world population is projected to grow, with estimates ranging from 6.9 billion to 13.1 billion;[16] the percentage of people living in the 101 larger cities is estimated to be 15% to 23%.[16]

The following 101 cities with the largest population projections for the years 2025, 2050, 2075, and 2100 are listed below.[16]

Rank City Projected
Population (millions)
2025
City Projected
Population (millions)
2050
City Projected
Population (millions)
2075
City Projected
Population (millions)
2100
1 Japan Tokyo 36.40 India Mumbai 42.40 Bangladesh Dhaka 57.86 Bangladesh Dhaka 76.50
2 India Mumbai 26.39 Bangladesh Dhaka 36.16 Nigeria Lagos 55.26 Tanzania Dar es Salaam 73.68
3 Bangladesh Dhaka 22.50 India Delhi 35.19 Democratic Republic of the Congo Kinshasa 54.51 India Mumbai 67.24
4 India Delhi 22.02 Democratic Republic of the Congo Kinshasa 35.00 India Delhi 49.34 Democratic Republic of the Congo Kinshasa 63.05
5 Brazil São Paulo 21.43 India Kolkata 33.04 India Kolkata 45.09 Malawi Lilongwe 57.43
6 Mexico Mexico City 21.01 Nigeria Lagos 32.63 Pakistan Karachi 43.37 India Delhi 57.33
7 United States New York 20.63 Japan Tokyo 32.62 India Mumbai 42.45 Malawi Blantyre 56.78
8 India Kolkata 20.56 Pakistan Karachi 31.70 Tanzania Dar es Salaam 37.49 Sudan Khartoum 56.59
9 China Shanghai 19.41 United States New York 24.77 Egypt Cairo 33.00 Niger Niamey 55.24
10 Pakistan Karachi 19.10 Mexico Mexico City 24.33 Philippines Manila 32.75 India Kolkata 52.40
11 Democratic Republic of the Congo Kinshasa 16.76 Philippines Manila 24.26 Afghanistan Kabul 32.67 Afghanistan Kabul 49.27
12 Argentina Buenos Aires 16.50 Egypt Cairo 24.04 Sudan Khartoum 30.68 Pakistan Karachi 49.06
13 Nigeria Lagos 15.80 Colombia Bogota 23.55 Kenya Nairobi 28.42 Kenya Nairobi 46.66
14 Egypt Cairo 15.56 Brazil São Paulo 22.83 Colombia Bogota 27.90 Chad N’Djamena 41.15
15 Colombia Bogota 15.21 China Shanghai 22.32 United States New York 27.19 Egypt Cairo 40.54
16 China Beijing 14.55 Argentina Buenos Aires 22.13 Argentina Buenos Aires 25.63 Philippines Manila 39.96
17 Philippines Manila 14.20 Pakistan Lahore 17.45 Japan Tokyo 24.64 Nigeria Lagos 38.54
18 United States Los Angeles 13.67 Afghanistan Kabul 17.09 Iraq Baghdad 24.39 Somalia Mogadishu 36.37
19 Brazil Rio de Janeiro 13.41 United States Los Angeles 16.42 Pakistan Lahore 23.88 Ethiopia Addis Ababa 35.82
20 Indonesia Jakarta 12.36 India Chennai 16.28 Ethiopia Addis Ababa 23.71 Zambia Lusaka 35.76
21 Turkey Istanbul 12.10 Sudan Khartoum 16.00 Mexico Mexico City 22.80 Iraq Baghdad 34.10
22 China Guangzhou 11.84 Tanzania Dar es Salaam 15.97 India Chennai 22.21 Uganda Kampala 31.41
23 Japan Osaka-Kobe 11.37 China Beijing 15.97 India Bangalore 21.31 Colombia Bogota 31.03
24 Russia Moscow 10.53 Indonesia Jakarta 15.92 Niger Niamey 20.37 Argentina Buenos Aires 30.26
25 Pakistan Lahore 10.51 India Bangalore 15.62 Uganda Kampala 20.23 United States New York 27.25
26 China Shenzhen 10.20 Iraq Baghdad 15.09 India Hyderabad 19.94 Pakistan Lahore 27.01
27 India Chennai 10.13 India Hyderabad 14.61 Brazil São Paulo 19.73 India Chennai 25.81
28 France Paris 10.04 Angola Luanda 14.30 United States Los Angeles 18.02 India Bangalore 24.77
29 United States Chicago 9.93 Brazil Rio de Janeiro 14.29 Nigeria Kano 17.69 Nigeria Kano 24.52
30 Iran Tehran 9.81 Kenya Nairobi 14.25 Angola Luanda 17.15 India Hyderabad 23.17
31 South Korea Seoul 9.74 Turkey Istanbul 14.18 India Ahmedabad 16.96 Senegal Dakar 21.18
32 India Bangalore 9.72 Ethiopia Addis Ababa 13.21 Yemen Sana'a 16.69 Nigeria Ibadan 20.53
33 Peru Lima 9.60 China Guangzhou 13.00 Somalia Mogadishu 15.94 Mozambique Maputo 20.39
34 China Wuhan 9.34 India Ahmedabad 12.43 Malawi Lilongwe 15.23 Yemen Sana’a 19.91
35 China Tianjin 9.24 Bangladesh Chittagong 12.21 Malawi Blantyre 15.06 India Ahmedabad 19.71
36 India Hyderabad 9.09 United States Chicago 11.93 Indonesia Jakarta 14.96 Rwanda Kigali 18.30
37 United Kingdom London 8.62 Vietnam Ho Chi Minh City 11.86 India Pune 14.91 United States Los Angeles 18.06
38 Thailand Bangkok 8.33 Peru Lima 11.57 Nigeria Ibadan 14.81 Mali Bamako 17.85
39 Hong Kong Hong Kong 8.31 China Shenzhen 11.20 Bangladesh Chittagong 14.73 India Pune 17.32
40 China Chongqing 8.28 France Paris 11.12 Senegal Dakar 14.56 Mexico Mexico City 17.25
41 Angola Luanda 8.24 Thailand Bangkok 11.08 Zambia Lusaka 14.52 Nigeria Abuja 16.28
42 Vietnam Ho Chi Minh City 8.15 Iran Tehran 11.00 Chad N'Djamena 14.48 Japan Tokyo 15.54
43 Iraq Baghdad 8.06 India Pune 10.92 Ivory Coast Abidjan 14.27 Madagascar Antananarivo 15.45
44 Sudan Khartoum 7.94 Ivory Coast Abidjan 10.71 China Shanghai 14.17 Guinea Conakry 14.79
45 India Ahmedabad 7.74 Nigeria Kano 10.44 Mali Bamako 13.54 Egypt Alexandria 14.73
46 Bangladesh Chittagong 7.64 China Wuhan 10.26 United States Chicago 13.09 Cambodia Phnom Penh 14.60
47 Afghanistan Kabul 7.18 Russia Moscow 10.24 Thailand Bangkok 12.55 India Surat 14.53
48 Brazil Salvador 7.03 Japan Osaka-Kobe 10.19 India Surat 12.51 Ivory Coast Abidjan 14.16
49 India Pune 6.80 China Tianjin 10.15 Madagascar Antananarivo 12.40 Angola Luanda 14.03
50 Vietnam Hanoi 6.75 Yemen Sana'a 10.05 Brazil Rio de Janeiro 12.35 Kenya Mombasa 14.01
51 Brazil Belo Horizonte 6.75 Vietnam Hanoi 9.83 Vietnam Ho Chi Minh City 12.32 Brazil São Paulo 13.77
52 Chile Santiago 6.31 United Kingdom London 9.75 Egypt Alexandria 11.99 Bangladesh Chittagong 13.37
53 Saudi Arabia Riyadh 6.28 South Korea Seoul 9.47 Nigeria Abuja 11.75 United States Chicago 13.12
54 United States Miami 6.27 Hong Kong Hong Kong 9.47 Burkina Faso Ouagadougou 11.70 Burkina Faso Ouagadougou 12.63
55 China Dongguan 6.16 Uganda Kampala 9.43 Turkey Istanbul 11.56 Thailand Bangkok 12.14
56 China Shenyang 6.16 India Surat 9.17 Peru Lima 11.35 India Kanpur 11.73
57 Ethiopia Addis Ababa 6.16 China Chongqing 9.09 Mozambique Maputo 10.92 Nigeria Kaduna 11.45
58 United States Philadelphia 6.13 Nigeria Ibadan 8.75 France Paris 10.87 Democratic Republic of the Congo Lubumbashi 11.07
59 Ivory Coast Abidjan 6.03 Egypt Alexandria 8.73 Guinea Conakry 10.63 Egypt Giza 11.01
60 Canada Toronto 5.95 Senegal Dakar 8.52 China Beijing 10.62 Pakistan Faisalabad 11.00
61 Spain Madrid 5.94 Myanmar Yangon 8.44 Iran Tehran 10.36 India Jaipur 10.95
62 Kenya Nairobi 5.87 Saudi Arabia Riyadh 8.09 Vietnam Hanoi 10.21 Democratic Republic of the Congo Mbuji-Mayi 10.72
63 Myanmar Yangon 5.87 Mali Bamako 7.63 India Kanpur 10.09 Indonesia Jakarta 10.17
64 India Surat 5.70 United States Miami 7.53 United Kingdom London 10.09 Liberia Monrovia 10.12
65 Tanzania Dar es Salaam 5.69 Brazil Salvador 7.49 Rwanda Kigali 9.79 India Lucknow 10.05
66 Egypt Alexandria 5.65 India Kanpur 7.39 Pakistan Faisalabad 9.73 Nigeria Benin City 9.66
67 United States Dallas-Fort Worth 5.42 United States Philadelphia 7.36 Democratic Republic of the Congo Lubumbashi 9.57 United Kingdom London 9.56
68 Mexico Tlaquepaque 5.37 Madagascar Antananarivo 7.26 Russia Moscow 9.51 France Paris 9.33
69 Mexico Tonala 5.37 Brazil Belo Horizonte 7.19 Hong Kong Hong Kong 9.46 India Nagpur 9.13
70 Mexico Zapopan 5.37 Pakistan Faisalabad 7.11 India Jaipur 9.43 Vietnam Ho Chi Minh City 9.05
71 China Chengdu 5.32 Canada Toronto 7.04 Myanmar Yangon 9.37 Peru Lima 9.05
72 China Xi'an 5.23 Nigeria Abuja 6.94 Democratic Republic of the Congo Mbuji-Mayi 9.27 Iraq Mosul 8.87
73 Spain Barcelona 5.18 India Jaipur 6.91 Egypt Giza 8.96 Brazil Rio de Janeiro 8.62
74 United States Atlanta 5.15 Burkina Faso Ouagadougou 6.90 Cambodia Phnom Penh 8.85 Russia Moscow 8.43
75 China Guiyang 5.11 Niger Niamey 6.79 India Lucknow 8.65 Yemen Al Hudaydah 8.42
76 Singapore Singapore 5.10 Chile Santiago 6.77 China Guangzhou 8.64 United States Miami 8.29
77 Nigeria Kano 5.06 China Dongguan 6.76 Kenya Mombasa 8.53 Togo Lomé 8.27
78 United States Houston 5.05 China Shenyang 6.76 United States Miami 8.27 Hong Kong Hong Kong 8.27
79 United States Boston 5.03 Somalia Mogadishu 6.57 Nigeria Kaduna 8.26 India Patna 8.17
80 Mexico Guadalajara 4.97 Egypt Giza 6.52 United States Philadelphia 8.09 Iran Tehran 8.17
81 Mexico Guadalupe 4.95 Spain Madrid 6.52 Ghana Accra 7.98 Ghana Accra 8.17
82 United States Washington DC 4.89 United States Dallas-Fort Worth 6.51 India Nagpur 7.86 Nigeria Port Harcourt 8.15
83 Australia Sydney 4.83 India Lucknow 6.34 Saudi Arabia Riyadh 7.76 United States Philadelphia 8.10
84 China Nanjing 4.77 Mexico Tlaquepaque 6.22 Japan Osaka-Kobe 7.69 Uzbekistan Tashkent 8.10
85 China Harbin 4.70 Mexico Tonala 6.22 Canada Toronto 7.59 Myanmar Yangon 8.02
86 Brazil Porto Alegre 4.63 Mexico Zapopan 6.22 South Korea Seoul 7.52 Cambodia Battambang 7.98
87 United States Detroit 4.61 United States Atlanta 6.19 China Shenzhen 7.44 Yemen Taiz 7.92
88 India Kanpur 4.60 Democratic Republic of the Congo Lubumbashi 6.15 Togo Lomé 7.25 Pakistan Rawalpindi 7.88
89 Turkey Ankara 4.59 Guinea Conakry 6.14 United States Dallas-Fort Worth 7.14 Nepal Kathmandu 7.82
90 Brazil Brasilia 4.58 United States Houston 6.06 Liberia Monrovia 7.08 Senegal Pikine 7.87
91 Algeria Algiers 4.50 United States Boston 6.04 Cameroon Douala 7.07 India Indore 7.66
92 Russia St. Petersburg 4.48 Democratic Republic of the Congo Mbuji-Mayi 5.95 Yemen Al Hudaydah 7.06 Nigeria Ogbomosho 7.64
93 Mexico Monterrey 4.41 Ghana Accra 5.94 India Patna 7.03 Cameroon Douala 7.64
94 Yemen Sana’a 4.38 Syria Aleppo 5.90 Pakistan Rawalpindi 6.97 Vietnam Hanoi 7.50
95 Brazil Recife 4.35 United States Washington DC 5.87 Nigeria Benin City 6.97 Republic of the Congo Brazzaville 7.45
96 China Changchun 4.34 China Chengdu 5.84 Syria Aleppo 6.88 Canada Toronto 7.44
97 India Jaipur 4.30 Australia Sydney 5.82 China Wuhan 6.82 Egypt Al Qalyubiyah 7.24
98 Pakistan Faisalabad 4.28 Mexico Guadalajara 5.76 United States Atlanta 6.79 Tajikistan Dushanbe 7.18
99 Australia Melbourne 4.24 India Nagpur 5.76 China Tianjin 6.75 Nigeria Maiduguri 7.17
100 Nigeria Ibadan 4.23 China Xi'an 5.75 United States Houston 6.66 United States Dallas-Fort Worth 7.16

See also[edit]

References[edit]

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  3. ^ a b c d e f g h i j k l "World Population Prospects: The 2015 Revision – Key Findings and Advance Tables" (PDF). United Nations Department of Economic and Social Affairs, Population Division. July 2015. Retrieved 26 June 2016. 
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  7. ^ Ciro Pabón y Ciro Pabón, Manual de Urbanismo, Editorial Leyer, Bogotá, 2007, ISBN 978-958-711-296-2
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  9. ^ Randers, Jørgen (2012). 2052: A Global Forecast for the Next Forty Years. Vermont: Chelsea Green Publishing. p. 62. 
  10. ^ Newmark, PA; Sánchez Alvarado, A (2002). "Not your father's planarian: a classic model enters the era of functional genomics". Nat Rev Genet. 3: 210–219. doi:10.1038/nrg759. PMID 11972158. 
  11. ^ Bavestrello, Giorgio; Sommer, Christian; Sarà, Michele (1992). "Bi-directional conversion in Turritopsis nutricula (Hydrozoa)". Scientia Marina. 56 (2–3): 137–140. 
  12. ^ Martínez, DE (1998). "Mortality patterns suggest lack of senescence in hydra". Exp Gerontol. 33 (3): 217–225. doi:10.1016/S0531-5565(97)00113-7. PMID 9615920. 
  13. ^ a b Andy Coghlan (27 Sep 2014). "Global population may boom well beyond the year 2050". New Scientist: 11. 
  14. ^ Patrick Gerland, Adrian Raftery; et al. (18 Sep 2014). "World population stabilization unlikely this century". Science. 346: 234–7. doi:10.1126/science.1257469. PMC 4230924free to read. PMID 25301627. 
  15. ^ Can we be sure the world's population will stop rising?, BBC News, 13 October 2012
  16. ^ a b c d e Hoornweg, Daniel; Pope, Kevin (January 2014). "Population predictions of the 101 largest cities in the 21st century" (PDF). Global Cities Institute (Working Paper No. 4).