World population estimates

This article lists estimates of world population over the course of history and prehistory, as well as projections of future developments. In summary, estimates for the progression of world population since the late medieval period are in the following ranges:

year 1400 1500 1600 1700 1800 1900 2000
population
(in millions)
350400 425500 500580 600680 890980 1,5601,710 6,0606,150

Estimates for pre-modern times are necessarily fraught with great uncertainties, and few of the published estimates have confidence intervals; in the absence of a straightforward means to assess the error of such estimates, a rough idea of expert consensus can be gained by comparing the values given in independent publications. Population estimates cannot be considered accurate to more than two decimal digits; for example, world population for the year 2012 was estimated at 7.02, 7.06 and 7.08 billion by the United States Census Bureau, the Population Reference Bureau and the United Nations Department of Economic and Social Affairs, respectively, corresponding to a spread of estimates of the order of 0.8%.

Deep prehistory

Most published estimates of historical world population begin at the beginning of the Common Era, when world population was in the nine digits (estimates range between 150 and 330 million).

Some estimates extend their timeline into deep prehistory, to "10,000 BC", i.e. the last glacial maximum,[1] when world population estimates range roughly between one and ten million.

Estimates for yet deeper prehistory, into the Upper Paleolithic, are of a different nature. At this time human populations consisted entirely of non-sedentary hunter-gatherer populations, which fall into a number of archaic species or sub-species, some but not all of which may be ancestral to the modern human population due to possible archaic human admixture with modern humans taking place during the Upper Paleolithic. Estimates of the size of these populations are a topic of paleoanthropology. A late human population bottleneck is postulated by some scholars at approximately 70,000 years ago, during the Toba catastrophe, when the Homo sapiens population may have dropped to as low as between 1,000 and 10,000 individuals.[2][3][4]

For the time of speciation of Homo sapiens, ca. 130,000 years ago, Sjödin et al. (2012) estimate an effective population size of the order of 10,000 to 30,000 individuals, inferring an actual "census population" of early Homo sapiens of roughly 100,000 to 300,000 individuals.[5]

Historical population

The following table uses astronomical year numbering for dates, negative numbers corresponding roughly to the corresponding year BC (i.e. -10000 = 10,001 BC, etc.). The table starts counting around the Late Glacial Maximum period, in which ice retreated and humans started to spread into the northern hemisphere.

Before 1950

Year Population Reference Bureau

(1973–2015)[6]

United Nations Department of Economic and Social Affairs

(2015)[7]

Maddison

(2008)[8]

HYDE

(2010)

Tanton

(1994)[9]

Biraben

(1980)[10]

McEvedy &

Jones (1978)[11]

Thomlinson

(1975)[12]

Durand

(1974)[13]

Clark

(1967)[14]

-100002M[15]4M1–10M
-90004M
-80005M5M5–10M
-70008M
-600011M
-500018M[15]5M5–20M
-400028M7M
-300045M14M
-200072M27M
-1000115M50M
-200150M
1300M300M231M[16]188M[15]150M255M170M200M270–330M256M[17]
100300M195M
200300M202M256M190M
300300M205M
350254M
400300M209M206M190M
500280M210M[15]206M190M
600300M213M206M200M237M
700310M226M207M210M
800330M240M224M220M261M
900360M269M226M240M
1000400M310M267M295M[15]254M265M275–345M280M
1100353M301M320M
1200450M393M400M360M384M
1250400M416M
1300500M392M300M432M360M400M
1340443M378M
1400440M390M374M350M
1500500M500M438M461M[15]460M425M440–540M427M
1600560M556M554M[15]579M545M498M
1650500M545M500M516M
1700660M603M603M[15]600M679M610M600M641M
1750795M791M814M770M720M700M735–805M731M
18001,000M978M989M[15]900M954M900M900M890M
18201,042M
18501,265M1,262M1,263M1,241M1,200M1,200M
18701,276M
18751,325M
19001,656M1,650M1,563M1,654M[15]1,600M1,633M1,625M1,600M1,650–1,710M1,668M
19101,750M1,777M
19131,793M
19201,860M1,863M1,912M1,968M
19252,000M
19302,070M2,092M2,145M
19402,300M2,299M2,307M2,340M

1950 to present

For times after World War II, demographic data of some accuracy becomes available for a significant number of countries, and population estimates are often given as grand totals of numbers (typically given by country) of widely diverging accuracies. Some sources give these numbers rounded to the nearest million or the nearest thousand, while others give them without any rounding. Taking these numbers at face value would be false precision; in spite of being stated to four, seven or even ten digits, they should not be interpreted as accurate to more than three digits at best.

Year United States Census Bureau

(2015)[18]

Population Reference Bureau

(1973–2015)[6]

United Nations Department of Economic and Social Affairs

(2015)[7]

Maddison

(2008)[8]

HYDE

(2007)[15]

Tanton

(1994)[9]

Biraben

(1980)[10]

McEvedy &

Jones (1978)[11]

Thomlinson

(1975)[12]

Durand

(1974)[13]

Clark

(1967)[14]

19502,557,628,6542,516,000,0002,525,149,0002,544,000,0002,527,960,0002,400,000,0002,527,000,0002,500,000,0002,400,000,0002,486,000,000
19512,594,939,8772,572,850,9172,571,663,000
19522,636,772,3062,619,292,0682,617,949,000
19532,682,053,3892,665,865,3922,665,959,000
19542,730,228,1042,713,172,0272,716,927,000
19552,782,098,9432,761,650,9812,769,074,000
19562,835,299,6732,811,572,0312,822,502,000
19572,891,349,7172,863,042,7952,879,934,000
19582,948,137,2482,916,030,1672,939,254,000
19593,000,716,5932,970,395,8142,995,909,000
19603,043,001,5083,026,002,9423,041,507,0003,042,000,000
19613,083,966,9293,082,830,2663,082,161,000
19623,140,093,2173,141,071,5313,135,787,0003,036,000,000
19633,209,827,8823,201,178,2773,201,354,000
19643,281,201,3063,263,738,8323,266,477,000
19653,350,425,7933,329,122,4793,333,138,000
19663,420,677,9233,397,475,2473,402,224,0003,288,000,000
19673,490,333,7153,468,521,7243,471,464,000
19683,562,313,8223,541,674,8913,543,086,000
19693,637,159,0503,616,108,7493,615,743,000
19703,712,697,7423,691,172,6163,691,157,0003,710,000,0003,637,000,0003,600,000,0003,600,000,000– 3,700,000,0003,632,000,000
19713,790,326,9483,766,754,3453,769,818,000
19723,866,568,6533,842,873,6113,846,499,000
19733,942,096,4423,919,182,3323,922,793,0003,923,000,0003,860,000,000
19744,016,608,8133,995,304,9223,997,677,000
19754,089,083,2334,071,020,4344,070,671,0003,900,000,0004,000,000,000
19764,160,185,0104,146,135,8504,141,445,000
19774,232,084,5784,220,816,7374,213,539,000
19784,304,105,7534,295,664,8254,286,317,000
19794,379,013,9424,371,527,8714,363,144,000
19804,451,362,7354,449,048,7984,439,529,0004,461,000,000
19814,534,410,1254,528,234,6344,514,838,000
19824,614,566,5614,608,962,4184,587,307,000
19834,695,736,7434,691,559,8404,676,388,000
19844,774,569,3914,776,392,8284,756,521,000
19854,856,462,6994,863,601,5174,837,719,0005,000,000,000
19864,940,571,2324,953,376,7104,920,968,000
19875,027,200,4925,045,315,8715,006,672,000
19885,114,557,1675,138,214,6885,093,306,000
19895,201,440,1105,230,000,0005,180,540,000
19905,288,955,9345,320,816,6675,269,029,0005,308,000,000
19915,371,585,9225,408,908,7245,351,922,000
19925,456,136,2785,494,899,5705,435,722,000
19935,538,268,3165,578,865,1095,518,127,000
19945,618,682,1325,661,086,3465,599,396,000
19955,699,202,9855,760,000,0005,741,822,4125,681,575,000
19965,779,440,5935,821,016,7505,762,212,000
19975,857,972,5435,840,000,0005,898,688,3375,842,122,000
19985,935,213,2485,975,303,6575,921,366,000
19996,012,074,9226,051,478,0105,999,622,000
20006,088,571,3836,067,000,0006,127,700,4286,076,558,0006,145,000,0005,750,000,000
20016,165,219,2476,137,000,0006,204,147,0266,154,791,000
20026,242,016,3486,215,000,0006,280,853,8176,231,704,000
20036,318,590,9566,314,000,0006,357,991,7496,308,364,000
20046,395,699,5096,396,000,0006,435,705,5956,374,056,000
20056,473,044,7326,477,000,0006,514,094,6056,462,987,000
20066,551,263,5346,555,000,0006,593,227,9776,540,214,000
20076,629,913,7596,625,000,0006,673,105,9376,616,689,000
20086,709,049,7806,705,000,0006,753,649,2286,694,832,000
20096,788,214,3946,809,972,0006,834,721,9336,764,086,000
20106,866,332,3586,892,319,0006,916,183,482
20116,944,055,5836,986,951,0006,997,998,760
20127,022,349,2837,057,075,0007,080,072,417
20137,101,027,8957,136,796,0007,162,119,434
20147,178,722,8937,238,184,0007,243,784,000
20157,256,490,0117,336,435,0007,349,472,000

Projections

World population estimates from 1800 to 2100, based on "high", "medium" and "low" United Nations projections in 2010 (colored red, orange and green) and US Census Bureau historical estimates (in black). Actual recorded population figures (as of 2010) are colored in blue. According to the highest estimate, the world population may rise to 16 billion by 2100; according to the lowest estimate, it may decline to 6 billion.

As of 2015, the population of the world is projected to reach 8 billion in 2025, and 9 billion by about 2040/42. Kapitza (1996) estimated an asymptotic limit of population growth of 14 billion, 90% of which (12.6 billion) expected to be reached by 2135.[19]

Reasonable predictions of population development are possible for the next 30 years or so, representing the period of fertility of the children alive today. Projections of population reaching more than one generation into the future are highly speculative: Thus, the United Nations Department of Economic and Social Affairs report of 2004 projected the world population to peak at 9.22 billion in 2075 and then stabilise at a value close to 9 billion;[20] By contrast, a 2014 projection by the United Nations Population Division predicts a population close to 11 billion by 2100 without any declining trend in the foreseeable future.[21] On the other hand, a conservative scenario published in 2012 assumes that a maximum of 8 billion will be reached before 2040.[22]

The following table shows projections of world population for the 21st century.

Year United States Census Bureau

(2015)[18]

Population Reference Bureau

(1973-2015)[6]

United Nations Department of Economic and Social Affairs

(2015)[7]

20167,334,771,6147,432,663,280
20177,412,778,971
20187,490,427,640
20197,567,402,977
20207,643,402,1237,758,157,000
20217,718,256,830
20227,792,021,317
20237,864,725,370
20247,936,271,554
20258,006,580,5538,000,000,0008,141,661,000
20268,075,716,000
20278,143,729,466
20288,210,559,895
20298,276,190,519
20308,340,606,5908,505,000,0008,500,766,000
20318,403,880,343
20328,466,094,022
20338,527,246,205
20348,587,325,154
20358,646,304,7048,838,908,000
20368,704,239,274
20378,761,189,197
20388,817,138,785
20398,872,066,537
20408,925,949,6799,157,234,000
20418,978,822,945
20429,030,723,366
20439,081,617,002
20449,131,462,326
20459,180,225,2149,453,892,000
20469,227,935,007
20479,274,616,811
20489,320,232,984
20499,364,750,182
20509,408,141,3029,804,000,0009,725,148,000
20559,968,809,000
206010,184,290,000
206510,375,719,000
207010,547,989,000
207510,701,653,000
208010,836,635,000
208510,953,525,000
209011,055,270,000
209511,142,461,000
210011,213,317,000

Other, historical projections include

By world region

Population estimates for world regions based on Maddison (2007),[23] in millions. The row showing total world population includes the average growth rate per year over the period separating each column from the preceding one.

year 1 1000 1500 1600 1700 1820 1913 2000 2030
East/Southeast Asia 74 (33%) 88 (33%) 156 (28%) 223 (37%) 216 (36%) 469 (45%) 613 (34%) 1,996 (33%) 2,417 (30%)
South Asia 75 (33%) 75 (28%) 110 (25%) 135 (24%)165 (27%) 216 (21%) 326 (18%) 1,372 (23%) 2,003 (25%)
Europe[24] 34 (15%) 40 (15%) 78 (18%) 112 (20%) 127 (21%) 224 (21%) 498 (28%) 742 (13%) 829 (11%)
West Asia 19 (8%) 20 (7%) 18 (3%) 21 (3%) 21 (3%) 25 (2%) 39 (2%) 237 (4%) 370 (5%)
Africa 17 (8%) 32 (12%) 47 (11%) 55 (10%) 61 (10%) 74 (7%) 125 (7%) 798 (13%) 1,449 (18%)
South/Central America 6 (3%) 11 (4%) 18 (4%) 9 (2%) 12 (2%) 22 (2%) 81 (5%) 520 (9%) 702 (9%)
North America 1 (0%) 1 (0%) 2 (0%) 2 (0%) 1 (0%) 11 (1%) 105 (6%) 314 (5%) 413 (5%)
World 226 267
(+ 0.02% p.a.)
438
(+ 0.1% p.a.)
556
(+ 0.2% p.a.)
603
(+ 0.1% p.a.)
1,041
(+ 0.5% p.a.)
1,791
(+ 0.6% p.a.)
6,062
(+ 1.4% p.a.)
8,175
(+ 1.0% p.a.)

See also

References

  1. Pala, M; Olivieri, A; Achilli, A; Accetturo, M; Metspalu, E; Reidla, M; Tamm, E; Karmin, M; Reisberg, T; Hooshiar Kashani, B; Perego, UA; Carossa, V; Gandini, F; Pereira, JB; Soares, P; Angerhofer, N; Rychkov, S; Al-Zahery, N; Carelli, V; Sanati, MH; Houshmand, M; Hatina, J; Macaulay, V; Pereira, L; Woodward, SR; Davies, W; Gamble, C; Baird, D; Semino, O; Villems, R; Torroni, A; Richards, MB (2012). "Mitochondrial DNA signals of late glacial recolonization of Europe from near eastern refugia". Am. J. Hum. Genet. 90: 915–24. PMC 3376494Freely accessible. PMID 22560092. doi:10.1016/j.ajhg.2012.04.003.
  2. Stanley H. Ambrose (1998). "Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans". Journal of Human Evolution. 34 (6): 623651. PMID 9650103. doi:10.1006/jhev.1998.0219.
  3. Ambrose, Stanley H. (2005). "Volcanic Winter, and Differentiation of Modern Humans". Bradshaw Foundation. Retrieved 2006-04-08.
  4. Robock, A., C.M. Ammann, L. Oman, D. Shindell, S. Levis, and G. Stenchikov (2009). "Did the Toba volcanic eruption of ~74k BP produce widespread glaciation?". Journal of Geophysical Research. 114 (D10): D10107. Bibcode:2009JGRD..11410107R. doi:10.1029/2008JD011652.
  5. Per Sjödin, Agnès E Sjöstrand, Mattias Jakobsson and Michael G B Blum, "Resequencing data provide no evidence for a human bottleneck in Africa during the penultimate glacial period" Mol Biol Evol (2012) doi: 10.1093/molbev/mss061. "A small human effective population size, on the order of 10,000 individuals, which is smaller than the effective population size of most great apes, has been interpreted as a result of a very long history, starting ∼ 2 mya, of a small population size, coined as the long-necked bottle model (Harpending et al. 1998; Hawks et al. 2000). Our findings are consistent with this hypothesis, but, depending on the mutation rate, we find either an effective population size of NA = 12,000 (95% C.I. = 9,000−15,500 when averaging over all three demographic models) using the mutation rate calibrated with the human-chimp divergence or an effective population size of NA = 32,500 individuals (95% C.I. = 27,500−34,500) using the mutation rate given by whole-genome trio analysis (The 1000 Genomes Project Consortium 2010) (supplementary figure 4 and table 6, Supplementary Material online). Not surprisingly, the estimated effective mutation rates θ = 4NAµ are comparable for the two mutation rates we considered, and are equal to 1.4 × 10−3/bp/generation (95% C.I. = (1.1−1.7) × 10−3). Relating the estimated effective population size to the census population size during the Pleistocene is a difficult task because there are many factors affecting the effective population size (Charlesworth 2009). Nevertheless, based on published estimates of the ratio between effective and census population size, a comprehensive value on the order of 10% has been found by Frankham (1995). This 10% rule roughly predicts that 120,000−325,[0]00 individuals (depending on the assumed mutation rate)"
  6. 1 2 3 Data from Population Reference Bureau.
    2015 estimate: (a) Toshiko Kaneda, 2015, "2015 World Population Data Sheet".
    2014 estimate: (b) Carl Haub, 2014, "2014 World Population Data Sheet".
    2013 estimate: (c) Carl Haub, 2013, "2013 World Population Data Sheet".
    2012 estimate: (d) Carl Haub, 2012, "2012 World Population Data Sheet".
    2011 estimate: (e) Carl Haub, 2011, "2011 World Population Data Sheet".
    2010 estimate: (f) Carl Haub, 2010, "2010 World Population Data Sheet".
    2009 estimate: (g) Carl Haub, 2009, "2009 World Population Data Sheet".
    2008 estimate: (h) Carl Haub, 2008, "2008 World Population Data Sheet".
    2007 estimate: (i) Carl Haub, 2007, "2007 World Population Data Sheet".
    2006 estimate: (j) Carl Haub, 2006, "2006 World Population Data Sheet".
    2005 estimate: (k) Carl Haub, 2005, "2005 World Population Data Sheet".
    2004 estimate: (l) Carl Haub, 2004, "2004 World Population Data Sheet".
    2003 estimate: (m) Carl Haub, 2003, "2003 World Population Data Sheet".
    2002 estimate: (n) Carl Haub, 2002, "2002 World Population Data Sheet".
    2001 estimate: (n) Carl Haub, 2001, "2001 World Population Data Sheet".
    2000 estimate: (p) 2000, "9 Billion World Population by 2050".
    1997 estimate: (q) 1997, "Studying Populations".
    Estimates for 1995 and prior: (r) Carl Haub, 1995, "How Many People Have Ever Lived on Earth?" Population Today, Vol. 23 (no. 2), pp. 5–6.
  7. 1 2 3 Data from United Nations Department of Economic and Social Affairs, Population Division.
    1950–2100 estimates (only medium variants shown): (a) World Population Prospects: The 2008 Revision.
    Estimates prior to 1950: (b) "The World at Six Billion", 1999.
    Estimates from 1950 to 2100: (c) "Population of the entire world, yearly, 1950 - 2100", 2013.
    2014: (d) http://esa.un.org/unpd/wup/Highlights/WUP2014-Highlights.pdf "2014 World Urbanization Prospects", 2014.]
    2015: (e) http://esa.un.org/unpd/wpp/Publications/Files/Key_Findings_WPP_2015.pdf "2015 World Urbanization Prospects", 2015.] Archived March 20, 2014, at the Wayback Machine.
  8. 1 2 Angus Maddison, 2003, The World Economy: Historical Statistics, Vol. 2, OECD, Paris ISBN 92-64-10412-7.
    "Statistical Appendix" (2008, ggdc.net) "The historical data were originally developed in three books: Monitoring the World Economy 1820-1992, OECD, Paris 1995; The World Economy: A Millennial Perspective, OECD Development Centre, Paris 2001; The World Economy: Historical Statistics, OECD Development Centre, Paris 2003. All these contain detailed source notes. Figures for 1820 onwards are annual, wherever possible. For earlier years, benchmark figures are shown for 1 AD, 1000 AD, 1500, 1600 and 1700." "OECD countries GDP revised and updated 1991-2003 from National Accounts for OECD Countries, vol. I, 2006. Norway 1820-1990 GDP from Ola Grytten (2004), “The Gross Domestic Product for Norway, 1830-2003” in Eitrheim, Klovland and Qvigstad (eds), Historical Monetary Statistics for Norway, 1819-2003, Norges Bank, Oslo. Latin American GDP 2000-2003 revised and updated from ECLAC, Statistical Yearbook 2004 and preliminary version of the 2005 Yearbook supplied by Andre Hofman. For Chile, GDP 1820-2003 from Rolf Lűders (1998), “The Comparative Economic Performance of Chile 1810-1995”, Estudios de Economia, vol. 25, no. 2, with revised population estimates from Diaz, J., R. Lűders, and G. Wagner (2005) Chili 1810-2000: la Republica en Cifras, mimeo, Instituto de Economia, Universidad Católica de Chile. For Peru, GDP 1896-1990 and population 1896-1949 from Bruno Seminario and Arlette Beltran, Crecimiento Economico en el Peru 1896-1995, Universidad del Pacifico, 1998. " "For Asia there are amendments to the GDP estimates for South and North Korea, 1911-74, to correct an error in Maddison (2003). Estimates for the Philippines, 1902-1940 were amended in line with Richard Hooley (2005), 'American Economic Policy in the Philippines, 1902-1940', Journal of Asian Economics, 16. 1820 estimates were amended for Hong Kong, the Philippines, Singapore, Sri Lanka, Taiwan and Thailand." "Asian countries GDP revised and updated 1998-2003 from Asian Development Bank, Key Indicators 2005, except for South Korea and Japan, where OECD sources were used for 1991-2003. GDP for African countries updated 2000-2003 from IMF, World Economic Outlook, April 2005. Population estimates for all countries except China and Indonesia revised and updated 1950-2008 and 2030 from International Data Base, International Programs Center, Population Division, US Bureau of the Census, April 2005 version. China’s population 1990-2003 from China Statistical Yearbook 2005, China Statistics Press, Beijing. Indonesian population 1950-2003 kindly supplied by Pierre van der Eng. The figures now include three countries previously omitted: Cook Islands, Nauru and Tuvalu."
  9. 1 2 3 John H. Tanton, 1994, "End of the Migration Epoch? Time For a New Paradigm", The Social Contract, Vol. 4 (no 3), pp. 162–173.
  10. 1 2 Slightly updated data from original paper in French: (a) Jean-Noël Biraben, 1980, "An Essay Concerning Mankind's Evolution", Population, Selected Papers, Vol. 4, pp. 1–13. Original paper in French: (b) Jean-Noël Biraben, 1979, "Essai sur l'évolution du nombre des hommes", Population, Vol. 34 (no. 1), pp. 13–25.
  11. 1 2 3 Colin McEvedy and Richard Jones, 1978, Atlas of World Population History, Facts on File, New York, ISBN 0-7139-1031-3.
  12. 1 2 Ralph Thomlinson, 1975, Demographic Problems: Controversy over population control, 2nd Ed., Dickenson Publishing Company, Ecino, CA, ISBN 0-8221-0166-1.
  13. 1 2 John D. Durand, 1974, "Historical Estimates of World Population: An Evaluation", University of Pennsylvania, Population Center, Analytical and Technical Reports, Number 10.
  14. 1 2 Colin Clark, 1967, Population Growth and Land Use, St. Martin's Press, New York, ISBN 0-333-01126-0.
  15. 1 2 3 4 5 6 7 8 9 10 11 Data from History Database of the Global Environment. K. Klein Goldewijk, A. Beusen and P. Janssen, "HYDE 3.1: Long-term dynamic modeling of global population and built-up area in a spatially explicit way", from table on pg. 2, Netherlands Environmental Assessment Agency (MNP), Bilthoven, The Netherlands.
  16. "The present figures are a revision and update of those presented on this website in 2003. The most significant changes are in the entries for the year 1, where gaps in previous tables have been filled with the new estimates for the Roman Empire in Maddison (2007). The estimates are in fact for 14 AD"
  17. The estimates are in fact for 14 AD"
  18. 1 2 Data from U.S. Census Bureau, International Data Base Retrieved on June 10, 2014
  19. "The expression for growth (6) indicates a limit for world population N=πK2=14×109, in the foreseeable future. Of this asymptotic limit 90% will be reached for Model III by year 2135, or in 3T years after T1 = 2007." Sergei P. Kapitza, 'The phenomenological theory of world population growth', Physics-Uspekhi 39(1) 57-71 (1996).
  20. United Nations Department of Economic and Social Affairs. World Population to 2300. 2004. Executive Summary, Page 2.
  21. Gerland, P.; Raftery, A. E.; Ev Ikova, H.; Li, N.; Gu, D.; Spoorenberg, T.; Alkema, L.; Fosdick, B. K.; Chunn, J.; Lalic, N.; Bay, G.; Buettner, T.; Heilig, G. K.; Wilmoth, J. (September 14, 2014). "World population stabilization unlikely this century". Science. AAAS. 346 (6206): 234–7. ISSN 1095-9203. PMC 4230924Freely accessible. PMID 25301627. doi:10.1126/science.1257469. Retrieved September 21, 2014.
  22. Randers, Jorgen (2012). 2052: A Global Forecast for the Next Forty Years. Vermont: Chelsea Green Publishing. p. 62.
  23. Angus Maddison, The World Economy: Historical Statistics, Statistical Appendix (2007, ggdc.net). Estimates cited are for the beginning of the 1st millennium ("year 0"), the beginning of the 2nd millennium ("year 1000"), and for the beginning each century since the 16th (years 1820 and 1913 are given for the 19th and 20th century, respectively, as Maddison presents detailed estimates for these years), and a projection for the year 2030.
  24. includes Central Asia (listed under "former USSR")

Further reading

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