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	Africa	Asia	Europe	Latin America	Northern America	Oceania
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	Africa	Asia	Europe	Latin America	Northern America	Oceania

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:

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:

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