# World population

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World population
World population estimates from 1800 to 2100, based on UN 2004 projections (red, orange, green) and US Census Bureau historical estimates (black).

The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be 6.976 billion by the United States Census Bureau.[1] According to a separate estimate by the United Nations, it has already exceeded 7 billion.[2][3][4] The world population has experienced continuous growth since the end of the Great Famine and Black Death in 1350, when it stood at around 370 million.[5] The highest rates of growth – global increases above 1.8% per year – were seen briefly during the 1950s, and for a longer period during the 1960s and 1970s. The growth rate peaked at 2.2% in 1963, and had declined to 1.1% by 2009. Annual births peaked at 173 million in the late 1990s, and are now expected to remain constant at their 2011 level of 134 million, while deaths number 56 million per year, and are expected to increase to 80 million per year by 2040.[6] Current projections show a continued increase in population (but a steady decline in the population growth rate), with the global population expected to reach between 7.5 and 10.5 billion by 2050.[7][8][9]

## Population by region

Population statistics for all six permanently inhabited continents and the ten most-populated countries.

The world's population is unevenly distributed, with six of the world's seven continents being permanently inhabited on a large scale. Asia is the most-populated of Earth's continents, with its 4.1 billion inhabitants accounting for over 60% of the world population. The world's two most-populated countries alone, China and India, constitute about 37% of the world's population. Africa is the second-most-populated continent, with around 1 billion people, or 15% of the world's population. Europe's 733 million people make up 11% of the world's population, while the Latin American and Caribbean regions are home to 589 million (9%). Northern America has a population of around 352 million (5%), and Oceania, the least-populated region, has about 35 million inhabitants (0.5%).[10] Though it is not permanently inhabited by any fixed population, Antarctica has a small, fluctuating international population, based mainly in polar science stations. This population tends to rise in the summer months and decrease significantly in winter, as visiting researchers return to their home countries.[11]

World population (millions)[12]
# Top ten most populous 1990 2008 2025*
1 China 1,141 1,333 1,458
2 India 849 1,140 1,398
3 US 250 304 352
4 Indonesia 178 228 273
5 Brazil 150 192 223
6 Pakistan 108 166 226
8 Nigeria 94 151 208
9 Russia 148 142 137
10 Japan 124 128 126
World total 5,265 6,688 8,004
Top ten most populous (%) 60.0 % 58.9 % 57.5 %
1 Asia 1,613 2,183 2,693
+ China 1,141 1,333 1,458
+ OECD Pacific* 187 202 210
2 Africa 634 984 1,365
3 Europe* 564 603 659
+ Russia 148 142 137
+ ex Soviet Union* 133 136 146
4 Latin America 355 462 550
5 North America* 359 444 514
6 Middle East 132 199 272
Australia 17 22 28
European Union – 27 states 473 499 539
US + Canada 278 338 392
Ex Soviet Union 289 285 289
Geographical definitions as in IEA Key Stats 2010 p.66
Notes:
• Europe = OECD Europe + Non-OECD Europe and
excluding Russia and including Estonia, Latvia and Lithuania
• ex Soviet Union (SU) = SU excluding Russia and Baltic states
• North America = US, Canada, Mexico
• OECD Pacific = Australia, Japan, Korea, New Zealand
• 2025 = with constant annual 2007/2008 growth until 2025

### Population by continent

Continent name Density (inhab./km2) Population (2011) Most populous country Most populous city
Asia 86.7 4,140,336,501  People's Republic of China (1,341,403,687) Tokyo (13,185,502)
Africa 32.7 994,527,534  Nigeria (152,217,341) Cairo (19,439,541)
Europe 70 738,523,843  Russia (142,905,200) Moscow (14,837,510)
North America 22.9 528,720,588  United States of America (308,745,538) Mexico City (21,163,226)
South America 21.4 385,742,554  Brazil (190,732,694) São Paulo (19,672,582)
Oceania 4.25 36,102,071  Australia (22,612,355) Sydney (4,575,532)
Antarctica 0 4,490 (varies)[13] N/A[14] McMurdo Station (955)[15]

## Milestones by the billions

World population milestones (USCB estimates)
Population
(in billions)
1 2 3 4 5 6 7 8 9
Year 1804 1927 1960 1974 1987 1999 2012 2027 2046
Years elapsed –– 123 33 14 13 12 13 15 19

It is estimated that the population of the world reached one billion for the first time in 1804. It would be another 122 years before it reached two billion in 1927, but it took only 33 years to rise by another billion people, reaching three billion in 1960. Thereafter, the global population reached four billion in 1974, five billion in 1987, six billion in 1999 and, by some estimates, seven billion in October 2011.[2] However, other estimates hold that the world population will not reach seven billion until early 2012.[1]

According to current projections, the global population will reach eight billion by 2025–2030, and will likely reach around nine billion by 2045–2050. Alternative scenarios for 2050 range from a low of 7.4 billion to a high of more than 10.6 billion.[16] Projected figures vary depending on underlying statistical assumptions and which variables are manipulated in projection calculations, especially the fertility variable. Long-range predictions to 2150 range from a population decline to 3.2 billion in the 'low scenario', to 'high scenarios' of 24.8 billion. One scenario predicts a massive increase to 256 billion by 2150, assuming fertility remains at 1995 levels.[17]

There is no estimation for the exact day or month the world's population surpassed each of the one and two billion marks. The days of three and four billion were not officially noted, but the International Database of the United States Census Bureau places them in July 1959 and April 1974. The United Nations did determine, and celebrate, the "Day of 5 Billion" on 11 July 1987, and the "Day of 6 Billion" on 12 October 1999. The "Day of 7 Billion" was declared by the Population Division of the United Nations to be 31 October 2011.[18]

### Regional milestones by the billions

The first of Earth's regions to attain a billion inhabitants was the Northern Hemisphere,[when?] followed shortly by the Eastern Hemisphere, well before the world total hit two billion. The first single continent to reach this milestone was Asia, followed by the sub-regions of East Asia and South Asia. China became the first country with a billion inhabitants in 1980, and was followed by India in 1999. The Western Hemisphere reached the one-billion milestone in the 2000s, and the population of Africa reached one billion in 2010. The next one-billion-inhabitants milestones expected by demographers are the Americas, with a current population of around 920 million, and the Southern Hemisphere and Sub-Saharan Africa, currently each with around 850 million people. It is not known when, or if, the current next contenders, Europe, Southeast Asia, and North America in that order, will each surpass 1 billion inhabitants.

Currently, only the Northern Hemisphere, Eastern Hemisphere, and Asia have reached the 2-billion, 3-billion or 4-billion-inhabitants mark.

## History

### Antiquity and Middle Ages

A dramatic population bottleneck is theorized for the period around 70,000 BC as a result of the Toba supervolcano eruption. After this time, and until the development of agriculture around the 11th millennium BC, it is estimated that the world population stabilized at about one million people whose subsistence entailed hunting and foraging, a lifestyle that by its nature ensured a low population density. The total world population probably never exceeded 15 million inhabitants before the invention of agriculture.[19] By contrast, it is estimated that more than 50–60 million people lived in the combined eastern and western Roman Empire (AD 300–400).[20]

The plague which first emerged during the reign of Justinian caused Europe's population to drop by around 50% between 541 and the 8th century.[21] The population of Europe was more than 70 million in 1340.[22] The Black Death pandemic in the 14th century may have reduced the world's population from an estimated 450 million to between 350 and 375 million in 1400.[23] It took roughly 200 years for Europe's population to regain its 1340 level.[24] China experienced a population decline from an estimated 123 million around 1200 to an estimated 65 million in 1393,[25] which was presumably due to a combination of Mongol invasions and plague.[26]

At the founding of the Ming Dynasty in 1368, China's population was reported to be close to 60 million; toward the end of the dynasty in 1644, it might have approached 150 million.[27][28] England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500.[29] New crops that had come to Asia and Europe from the Americas via the Spanish colonizers in the 16th century are believed to have contributed to population growth.[30][31] Since being introduced by Portuguese traders in the 16th century,[32] maize and manioc have replaced traditional African crops as the continent’s most important staple food crops.[33] Alfred W. Crosby speculated that increased production of maize, manioc, and other American crops "...enabled the slave traders [who] drew many, perhaps most, of their cargoes from the rain forest areas, precisely those areas where American crops enabled heavier settlement than before."[34]

The population of the Americas in 1500 may have been between 50 and 100 million.[35] The pre-Columbian North American population probably numbered somewhere between 2 million and 18 million.[36] Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence.[37] Archaeological evidence indicates that the death of around 90% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza.[38] Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.[39]

### Modern era

Map showing urban areas with at least one million inhabitants in 2006. Only 3% of the world's population lived in cities in 1800; this proportion had risen to 47% by the end of the twentieth century, and reached 50.5% by 2010.[40]

During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically.[41] The percentage of the children born in London who died before the age of five decreased from 74.5% in 1730–1749 to 31.8% in 1810–1829.[42][43] Between 1700 and 1900, Europe’s population increased from about 100 million to over 400 million.[44] Altogether, the areas of European settlement comprised 36% of the world's population in 1900.[45]

Population growth in the West became more rapid after the introduction of compulsory vaccination and improvements in medicine and sanitation.[46][47][48] As living conditions and health care improved during the 19th century, the United Kingdom's population doubled every fifty years.[49] By 1801 the population of England had grown to 8.3 million, and by 1901 it had reached 30.5 million.[50]

The first half of the 20th century in Russia and the Soviet Union were marked by a succession of disasters, each accompanied by large–scale population losses.[51] By the end of World War II in 1945, therefore, the Russian population was about 90 million fewer than it could have been otherwise.[52]

The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941.[53] Today, the region is home to over 1.22 billion people.[54] The total number of inhabitants of Java increased from about five million in 1815 to more than 130 million in the early 21st century.[55] Mexico's population grew from 13.6 million in 1900 to about 112 million in 2009.[56] Between the 1920s and 2000s, Kenya's population grew from 2.9 million to 37 million.[57]

## Overpopulation

The scientific consensus is that the current population expansion and accompanying increase in usage of resources is linked to threats to the ecosystem.[58][59] The InterAcademy Panel Statement on Population Growth, which was ratified by 58 member national academies in 1994, called the growth in human numbers "unprecedented", and stated that many environmental problems, such as rising levels of atmospheric carbon dioxide, global warming, and pollution, were aggravated by the population expansion.[60] At the time, the world population stood at 5.5 billion, and lower-bound scenarios predicted a peak of 7.8 billion by 2050, a number that current estimates show will be reached around 2030.[61]

### Population control

Human population control is the practice of artificially altering the rate of growth of a human population. Historically, human population control has been implemented by limiting the population's birth rate, by contraception or by government mandate, and has been undertaken as a response to factors including high or increasing levels of poverty, environmental concerns, religious reasons, and overpopulation. The use of abortion in some strategies has made human population control a controversial issue, with organisations such as the Roman Catholic Church explicitly opposing the artificial limitation of the human population.[62]

## Largest populations by country

A map of the world's countries by total population.
The 10 countries with the largest total population:
Rank Country / Territory Population Date  % of world
population
Source
1  People's Republic of China[63] 1,347,570,000 November 22, 2011 19.3% Chinese Official Population Clock
2  India 1,203,710,000 March 2011 17% Census of India Organisation
3  United States 312,648,000 November 22, 2011 4.48% United States Official Population Clock
4  Indonesia 238,400,000 May 2010 3.36% SuluhNusantara Indonesia Census report
5  Brazil 195,566,000 November 22, 2011 2.8% Brazilian Official Population Clock
6  Pakistan 177,880,000 November 22, 2011 2.55% Official Pakistani Population Clock
7  Bangladesh 158,570,535 July 2011 2.27% 2011 CIA World Factbook estimate
8  Nigeria 155,215,000 July 2011 2.22% 2011 CIA World Factbook estimate
9  Russia 141,927,297 January 1, 2010 2.034% Federal State Statistics Service of Russia
10  Japan 127,380,000 June 1, 2010 1.83% Official Japan Statistics Bureau

Approximately 4.03 billion people live in these ten countries, representing 58.7% of the world's population as of November 2010.

## Most densely populated countries

Map showing global population density (people per km2) in 1994. Red areas show regions of highest population density.
The 10 most densely populated countries (with population above 1 million)
Rank Country/Region Population Area (km2) Density
(Pop per km2)
Notes
1  Singapore 5,183,700 707.1 7,331
2  Bangladesh 142,325,250 147,570 1,069 [64]
3  Mauritius 1,288,000 2,040 631 [65]
4  Palestinian territories 4,223,760 6,020 702
5  Republic of China 22,955,395 36,190 640 [66]
6  South Korea 48,456,369 99,538 487 [65][67]
7  Lebanon 4,224,000 10,452 404 [65]
8  Netherlands 16,740,000 41,526 403 [68]
9  Rwanda 9,998,000 26,338 380 [65]
10  Israel 7,697,600 20,770 371 [69]
Countries ranking in the top in terms of both total population (more than 15 million people) and population density (more than 250 people per square kilometer):
Country Population Area (km2) Density
(Pop. per km2)
Notes
India 1,205,910,000 3,287,240 367 Growing country
Bangladesh 142,325,250 143,998 1,069 Fast growing country
Japan 127,170,110 377,873 337 Declining in population
Philippines 94,013,200 300,076 313 Fast growing country
Vietnam 85,789,573 331,689 259 Growing country
United Kingdom 62,041,708 243,610 255 Growing country
South Korea 49,354,980 99,538 493 Steady in population
Republic of China 22,955,395 35,980 640 Steady in population
Sri Lanka 20,238,000 65,610 309 Growing country
Netherlands 16,740,000 41,526 403 Steady in population

## Demographics

As of 2011, the global sex ratio is approximately 1.01 males to 1 woman – the slightly higher number of men is possibly due to the gender imbalances evident in the Indian and Chinese populations.[70] Approximately 26.3% of the global population is aged under 15, while 65.9% is aged 15-64 and 7.9% is aged 65 or over.[70] The global average life expectancy is 67.07 years,[70] with women living an average of 69 years and men approximately 65 years.[70] 83% of the world's over-15s are considered literate.[70]

The Han Chinese are the world's largest ethnic group, constituting over 19% of the global population.[71] The world's most-spoken first languages are Mandarin Chinese (spoken by 12.44% of the world's population), Spanish (4.85%), English (4.83%), Arabic (3.25%) and Hindi (2.68%).[70] The world's largest religion is Christianity, whose adherents account for 33.35% of the global population; Islam is the second-largest, accounting for 22.43%, and Hinduism the third, accounting for 13.78%.[70]

## Growth

Population evolution in different continents, as recorded by the United Nations. The vertical axis is logarithmic and is in millions of people.

Different geographical regions have different rates of population growth. According to the United Nations, the growth in population of the different regions of the world from 2000 to 2005 was:

During the 20th century, the world saw the greatest increase in its population in human history. This was due to a number of factors, including the lessening of the mortality rate in many countries by improved sanitation and medical advances, and a massive increase in agricultural productivity attributed to the Green Revolution.[72][73][74]

In 2000, the United Nations estimated that the world's population was growing at an annual rate of 1.14% (equivalent to around 75 million people),[75] down from a peak of 88 million per year in 1989. By 2000, there were approximately ten times as many people on Earth as there had been in 1700. According to data from the CIA's 2005–2006 World Factbooks, the world human population increased by an average of 203,800 people every day in the mid-2000s.[76] The CIA Factbook increased this to 211,090 people every day in 2007, and again to 220,980 people every day in 2009.

A world map showing countries by fertility rate, 2005–2010.[citation needed]
 7–8 Children   6–7 Children 5–6 Children   4–5 Children 3–4 Children   2–3 Children 1–2 Children   0–1 Children

Globally, the population growth rate has been steadily declining from its peak of 2.19% in 1963, but growth remains high in Latin America, the Middle East and Sub-Saharan Africa.[77]

In some countries, there is negative population growth (i.e. net decrease in population over time), especially in Central and Eastern Europe – this is mainly due to low fertility rates. During the 2010s, Japan and some countries in Western Europe are also expected to encounter negative population growth, due to sub-replacement fertility rates.

In 2006, the United Nations stated that the rate of population growth is diminishing due to the ongoing global demographic transition. If this trend continues, the rate of growth may diminish to zero by 2050, concurrent with a world population plateau of 9.2 billion.[78] However, this is only one of many estimates published by the UN. In 2009, UN population projections for 2050 ranged from about 8 billion to 10.5 billion.[79]

### Forecasts

UN (medium variant, 2010 rev.) and US Census Bureau (December 2010) estimates[80][81]
Year UN est
(millions)
Diff. US est
(millions)
Diff.
2000 6,123 6,090
2010 6,896 773 6,852 763
2020 7,657 761 7,593 740
2030 8,321 665 8,249 656
2040 8,874 553 8,801 552
2050 9,306 432 9,256 456

In the long run, the future population growth of the world is difficult to predict. The United Nations and the US Census Bureau both give different estimates. According to the latter, world population will hit seven billion in July 2012,[82] while the UN asserted that this occurred in late 2011.[9]

Average global birth rates are declining slightly, but vary greatly between developed countries (where birth rates are often at or below replacement levels) and developing countries (where birth rates typically remain high). Different ethnicities also display varying birth rates. Death rates can change unexpectedly due to disease, wars and other mass catastrophes, or advances in medicine.

The UN has issued multiple projections of future world population, based on different assumptions. From 2000 to 2005, the UN consistently revised these projections downward, until the 2006 revision, issued on March 14, 2007, revised the 2050 mid-range estimate upwards by 273 million.

According to 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, where overpopulation would compromise global food security, leading to mass starvation.

UN 2008 estimates and medium variant projections (in millions)[83]
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%)

### Growth in population by region

The table below shows historical and predicted regional population figures in millions.[83][84][85][86] The availability of historical population figures varies by region.

World historical and predicted populations (in millions)[87][88][citation needed]
Region 1500 1600 1700 1750 1800 1850 1900 1950 1999 2008 2050 2150
World 458 580 682 791 978 1,262 1,650 2,521 5,978 6,707 8,909 9,746
Africa 86 114 106 106 107 111 133 221 767 973 1,766 2,308
Asia 243 339 436 502 635 809 947 1,402 3,634 4,054 5,268 5,561
Europe 84 111 125 163 203 276 408 547 729 732 628 517
Latin America and the Caribbean[Note 1] 39 10 10 16 24 38 74 167 511 577 809 912
Northern America[Note 1] 3 3 2 2 7 26 82 172 307 337 392 398
Oceania 3 3 3 2 2 2 6 13 30 34 46 51
World historical and predicted populations by percentage distribution [87][88][citation needed]
Region 1500 1600 1700 1750 1800 1850 1900 1950 1999 2008 2050 2150
World 100 100 100 100 100 100 100 100 100 100 100 100
Africa 18.8 19.7 15.5 13.4 10.9 8.8 8.1 8.8 12.8 14.5 19.8 23.7
Asia 53.1 58.4 63.9 63.5 64.9 64.1 57.4 55.6 60.8 60.4 59.1 57.1
Europe 18.3 19.1 18.3 20.6 20.8 21.9 24.7 21.7 12.2 10.9 7.0 5.3
Latin America and the Caribbean[Note 1] 8.5 1.7 1.5 2.0 2.5 3.0 4.5 6.6 8.5 8.6 9.1 9.4
Northern America[Note 1] 0.7 0.5 0.3 0.3 0.7 2.1 5.0 6.8 5.1 5.0 4.4 4.1
Oceania 0.7 0.5 0.4 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)[citation needed]
Year World Africa Asia Europe Latin America[Note 1] Northern America Oceania Notes
70,000 BC < 0.015 [89]
10,000 BC 1
9000 BC 3
8000 BC 5 [90]
7000 BC 7
6000 BC 10
5000 BC 15
4000 BC 20
3000 BC 25
2000 BC 35
1000 BC 50 [90]
500 BC 100 [90]
1000 310
1750 791 106 502 163 16 2 2
1800 978 107 635 203 24 7 2
1850 1,262 111 809 276 38 26 2
1900 1,650 133 947 408 74 82 6
1950 2,519 221 1,398 547 167 172 12.8
1955 2,756 247 1,542 575 191 187 14.3
1960 2,982 277 1,674 601 209 204 15.9
1965 3,335 314 1,899 634 250 219 17.6
1970 3,692 357 2,143 656 285 232 19.4
1975 4,068 408 2,397 675 322 243 21.5
1980 4,435 470 2,632 692 361 256 22.8
1985 4,831 542 2,887 706 401 269 24.7
1990 5,263 622 3,168 721 441 283 26.7
1995 5,674 707 3,430 727 481 299 28.9
2000 6,070 796 3,680 728 520 316 31.0
2005 6,454 888 3,917 725 558 332 32.9
2010 6,972 1,022 4,252 732 580 351 35.6 [4]
Year World Africa Asia Europe Latin America Northern America Oceania Notes
1. ^ a b c d e Northern America comprises the northern-most countries and territories of North America: Canada, the United States, Greenland, Bermuda, and St. Pierre and Miquelon. Latin America comprises Mexico, Central America, the Caribbean and South America.

The figures for North America only refer to post-European contact settlers, and not native populations from before European settlement.

## Mathematical approximations

Hoerner (1975) proposed a formula for population growth[93] which represented hyperbolic growth with an infinite population in 2025.

According to Kapitsa (1997),[94] the world population grew between 67,000 BC and 1965 according to the following formula:

$N = \frac{C}{\tau} \arccot \frac{T_0-T}{\tau}$

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 hyperbolic growth to slower rates of growth is related to the demographic transition.

### Years for world population to double

Using linear interpolation of UNDESA population estimates, the world population has doubled, or will double, in the following years (with two different starting points). Note how, during the 2nd millennium, each doubling took 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 of the global population in the 21st century.[95]

Historic chart showing the periods of time the world population has taken to double.
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

## Forecasts of scarcity

In 1798, the economist Thomas Malthus incorrectly predicted that population growth would out-run food supply by the mid-19th century. In 1968, Paul R. Ehrlich reprised this argument in The Population Bomb, predicting famine in the 1970s and 1980s. The dire predictions of Ehrlich and other neo-Malthusians were vigorously challenged by a number of economists, notably Julian Lincoln Simon. Agricultural research already under way, such as the Green Revolution, led to dramatic improvements in crop yields. Food production has so far kept pace with population growth, but Malthusians point out that the Green Revolution relies heavily on petroleum-based fertilizers, and that many crops have become so genetically uniform that a crop failure could potentially have global repercussions. Food prices in the early 21st century are rising sharply on a global scale, and causing serious malnutrition to spread widely.[96]

Graph of the global human population from 10,000 BC to 2000 AD, from the US Census Bureau. The graph shows the extremely rapid growth in the world population that has taken place over the past two centuries.

From 1950 to 1984, as the Green Revolution transformed agriculture around the world, grain production increased by over 250%.[97] The world population has grown by about four billion since the beginning of the Green Revolution and most believe that, without the Revolution, there would be greater famine and malnutrition than the UN presently documents (approximately 850 million people suffering from chronic malnutrition in 2005).[98] The energy for the Green Revolution was provided by fossil fuels, in the form of natural gas-derived fertilizers, oil-derived pesticides, and hydrocarbon-fueled irrigation.[99]

The potential peaking of world oil production may test the critics of Malthus and Ehrlich, as oil is of crucial importance to global transportation, power generation and agriculture.[100] In May 2008, the price of grain was pushed up severely by the increased cultivation of biofuels,[101] the increase of world oil prices to over $140 per barrel ($880/m3),[102] global population growth,[103] the effects of climate change,[104] the loss of agricultural land to residential and industrial development,[105][106] and growing consumer demand in the population centres of China and India.[107][108] Food riots subsequently occurred in some countries across the world.[109] However, oil prices then fell sharply, and remaining below \$100/barrel until around 2010. Resource demands are expected to ease as population growth declines, but it is unclear whether rising living standards in developing countries will once again create resource shortages.[110]

Richard C. Duncan claims the that the world population will decline to about 2 billion around 2050.[111] David Pimentel, professor of ecology and agriculture at Cornell University, estimates that the sustainable agricultural carrying capacity for the United States is about 200 million people; its population as of 2011 is over 310 million.[112] In 2009, the UK government's chief scientific advisor, Professor John Beddington, warned that growing populations, falling energy reserves and food shortages would create a "perfect storm" by 2030. Beddington claimed that food reserves were at a fifty-year low, and that the world would require 50% more energy, food and water by 2030.[113][114] According to a 2009 report by the United Nations Food and Agriculture Organisation (FAO), the world will have to produce 70% more food by 2050 to feed a projected extra 2.3 billion people.[115]

The observed figures for 2007 showed an actual increase in absolute numbers of undernourished people in the world, with 923 million undernourished in 2007, versus 832 million in 1995.[116] The 2009 FAO estimates showed an even more dramatic increase, to 1.02 billion.[117]

## Number of humans who have ever lived

An estimate of the total number of people who have ever lived was prepared by Carl Haub of the nonprofit Population Reference Bureau in 1995, and subsequently updated in 2002; the updated figure totalled approximately 106 billion.[118][119] Haub characterized this figure as an estimate that required "selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period".[119] Given an estimated global population of 6.2 billion in 2002, it could be inferred that about 6% of all people who had ever existed were alive in 2002.[118] Various estimates published in the first decade of the 21st century give figures ranging from approximately 100 billion to 115 billion.

In the 1970s, claims emerged that 75% of all the people who had ever lived were alive in the 1970s. This would mean that significantly more people would be alive in 2011 than had ever lived before. This view was eventually debunked as unscientific.[120]

An accurate estimate of the number of people who have ever lived is difficult to produce for the following reasons:

• The set of specific characteristics that define a human is a matter of definition, and it is open to debate which members of early Homo sapiens and earlier or related species of Homo to include in the estimate (see also Sorites paradox). Even if the scientific community reached a broad consensus regarding which characteristics distinguished human beings, it would be nearly impossible to pinpoint the time of their first appearance to even the nearest millennium, due to the scarcity of fossil evidence. However, the very limited size of the world population in prehistoric times (as compared to its current size) makes this source of uncertainty of limited importance.
• Robust statistical data only exist for the last two or three centuries. Until the late 18th century, few governments had ever performed an accurate census. In many early attempts, such as Ancient Egypt and in the Persian Empire the focus was on counting merely a subset of the people for purposes of taxation or military service.[121] All claims of population sizes preceding the 18th century are estimates, and thus the margin of error for the total number of humans who have ever lived should be in the billions, or even tens of billions of people.
• A critical factor for such an estimate is life expectancy. Using an average figure of twenty years and the population estimates above, one can compute about fifty-eight billion. Using a figure of forty yields half of that. Life expectancy varies greatly when taking into account children who died within the first year of birth, a number very difficult to estimate for earlier times. Haub states that "life expectancy at birth probably averaged only about ten years for most of human history"[119] His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond one year.

## United Nations population agencies

The United Nations operates several organisations with various population-related competencies, including the Commission on Population and Development, the United Nations Population Division, and the United Nations Population Fund.

Historical:

Lists:

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