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## Monday, June 21, 2010

### FORECAST

 UN (medium variant, 2008 rev.) and US Census Bureau (January 2010) estimates Year UN est (millions) Diff. US est (millions) Diff. 2000 6,115 - 6,084 - 2010 6,909 794 6,831 747 2020 7,675 766 7,558 727 2030 8,309 634 8,202 644 2040 8,801 492 8,749 547 2050 9,150 349 9,202 453

In the long run, the future population growth of the world is difficult to predict and the UN and US Census Bureau give different estimates. According to the latter, world population will hit seven billion in July 2012 or by late 2011, according to UN prediction.
Birth rates are declining slightly on average, but vary greatly between developed countries (where birth rates are often at or below replacement levels), developing countries, and different ethnicities. Death rates can change unexpectedly due to disease, wars and catastrophes, or advances in medicine.
The UN has issued multiple projections of future world population, based on different assumptions. Over the last ten years, the UN has consistently revised these projections downward, until the 2006 revision issued March 14, 2007 revised the 2050 mid-range estimate upwards by 273 million.
In some scenarios, disasters triggered by the growing population's demand for scarce resources will eventually lead to a sudden population crash, or even a Malthusian catastrophe (also see overpopulation and food security).
 UN 2008 estimates and medium variant projections (in millions). Year World Asia Africa Europe Latin America Northern America Oceania 2000 6,115 3,698 (60.5%) 819 (13.4%) 727 (11.9%) 521 (8.5%) 319 (5.2%) 31 (0.5%) 2005 6,512 3,937 (60.5%) 921 (14.1%) 729 (11.2%) 557 (8.6%) 335 (5.1%) 34 (0.5%) 2010 6,909 4,167 (60.3%) 1,033 (15.0%) 733 (10.6%) 589 (8.5%) 352 (5.1%) 36 (0.5%) 2015 7,302 4,391 (60.1%) 1,153 (15.8%) 734 (10.1%) 618 (8.5%) 368 (5.0%) 38 (0.5%) 2020 7,675 4,596 (59.9%) 1,276 (16.6%) 733 (9.6%) 646 (8.4%) 383 (5.0%) 40 (0.5%) 2025 8,012 4,773 (59.6%) 1,400 (17.5%) 729 (9.1%) 670 (8.4%) 398 (5.0%) 43 (0.5%) 2030 8,309 4,917 (59.2%) 1,524 (18.3%) 723 (8.7%) 690 (8.3%) 410 (4.9%) 45 (0.5%) 2035 8,571 5,032 (58.7%) 1,647 (19.2%) 716 (8.4%) 706 (8.2%) 421 (4.9%) 46 (0.5%) 2040 8,801 5,125 (58.2%) 1,770 (20.1%) 708 (8.0%) 718 (8.2%) 431 (4.9%) 48 (0.5%) 2045 8,996 5,193 (57.7%) 1,887 (21.0%) 700 (7.8%) 726 (8.1%) 440 (4.9%) 50 (0.6%) 2050 9,150 5,231 (57.2%) 1,998 (21.8%) 691 (7.6%) 729 (8.0%) 448 (4.9%) 51 (0.6%)

### FORECASTS BY REGION

Below is a table with historical and predicted population figures shown in millions.
The availability of historical population figures varies by region.
 World historical and predicted populations (in millions) Region 1750 1800 1850 1900 1950 1999 2008 2050 2150 World 791 978 1,262 1,650 2,521 5,978 6,707 8,909 9,746 Africa 106 107 111 133 221 767 973 1,766 2,308 Asia 502 635 809 947 1,402 3,634 4,054 5,268 5,561 Europe 163 203 276 408 547 729 732 628 517 Latin America and the Caribbean 16 24 38 74 167 511 577 809 912 Northern America 2 7 26 82 172 307 337 392 398 Oceania 2 2 2 6 13 30 34 46 51

 World historical and predicted populations by percentage distribution Region 1750 1800 1850 1900 1950 1999 2008 2050 2100 World 100 100 100 100 100 100 100 100 100 Africa 13.4 10.9 8.8 8.1 8.8 12.8 14.5 19.8 23.7 Asia 63.5 64.9 64.1 57.4 55.6 60.8 60.4 59.1 57.1 Europe 20.6 20.8 21.9 24.7 21.7 12.2 10.9 7.0 5.3 Latin America and the Caribbean 2.0 2.5 3.0 4.5 6.6 8.5 8.6 9.1 9.4 Northern America 0.3 0.7 2.1 5.0 6.8 5.1 5.0 4.4 4.1 Oceania 0.3 0.2 0.2 0.4 0.5 0.5 0.5 0.5 0.5

 Estimated world population at various dates (in millions) Year World 70,000 BCE < 1 10,000 BCE 1 9000 BCE 3 8000 BCE 5 7000 BCE 7 6000 BCE 10 5000 BCE 15 4000 BCE 20 3000 BCE 25 2000 BCE 35 1000 BCE 50 500 BCE 100 1 CE 200 1000 CE 310 1750 CE 791 106 502 163 16 2 2 1800 CE 978 107 635 203 24 7 2 1850 CE 1,262 111 809 276 38 26 2 1900 CE 1,650 133 947 408 74 82 6 1950 CE 2,519 221 1,398 547 167 172 12.8 1955 CE 2,756 247 1,542 575 191 187 14.3 1960 CE 2,982 277 1,674 601 209 204 15.9 1965 CE 3,335 314 1,899 634 250 219 17.6 1970 CE 3,692 357 2,143 656 285 232 19.4 1975 CE 4,068 408 2,397 675 322 243 21.5 1980 CE 4,435 470 2,632 692 361 256 22.8 1985 CE 4,831 542 2,887 706 401 269 24.7 1990 CE 5,263 622 3,168 721 441 283 26.7 1995 CE 5,674 707 3,430 727 481 299 28.9 2000 CE 6,070 796 3,680 728 520 316 31.0 2005 CE 6,454 888 3,917 725 558 332 32.9 Jul. 1, 2008 6,707 973 4,054 732 577 337 34.3 Year World
The figures for North and Central America only refer to post-European contact settlers, and not native populations from before European settlement.

### MATHEMATICAL APPROXIMATIONS

However (1975) proposed the following formula:
$N = \frac{C}{T_0-T}$
where
§     N is current population
§     T is the current year
§     C = 2·1011
§     T0 = 2025
which represents hyperbolic growth with an infinite population in 2025.
According to Kapitsa (1997), the population grew between 67,000 BC and 1965, and the world population growth formula is:
$N = \frac{C}{\tau} \arccot \frac{T_0-T}{\tau}$
where
§         N is current population
§         T is the current year
§         C = (1.86±0.01)·1011
§         T0 = 2007±1
§         τ = 42±1
The transition from hyperboles to slower rates of growth is related to the demographic transition.

#### YEARS FOR WORLD POPULATION TO DOUBLE

Using linear interpolation of the UNDESA estimates, the world population has been doubled or will double in the following years (with two different starting points). Note how, during the 2nd millennium, each doubling has taken roughly half as long as the previous doubling, fitting the hyperbolic growth model mentioned above. However, it is unlikely that there will be another doubling in the current century.
 Starting at 500 million Population (in billions) 0.5 1 2 4 8 Year 1500 1804 1927 1974 2025 Years elapsed 304 123 47 51

 Starting at 375 million Population (in billions) 0.375 0.75 1.5 3 6 Year 1171 1715 1881 1960 1999 Years elapsed 544 166 79 39