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 totality of all living humans on the planet Earth. As of today, it is estimated to number 6.993 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 2011. Total annual births were highest in the late 1980s at about 138 million,^[6] and are now expected to remain essentially 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.^[7] 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.^[8][9][10]

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 Earth's seven continents being permanently inhabited on a large scale. As of 2012^[update], Asia is the most-populated continent, 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%).^[12] 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.^[13]

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 (35,676,000)
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)[14]	N/A[15]	McMurdo Station (955)[16]

Milestones by the billions

It is estimated that the population of the world reached one billion for the first time in 1804. It would be another 123 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, according to a United Nations estimate, seven billion in October 2011.^[2][3][4] However, the United States Census Bureau holds 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.^[17] 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.^[18]

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.^[19]

Regional milestones by the billions

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The first of Earth's regions to attain a billion inhabitants was the Northern Hemisphere, 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 areas expected by demographers to exceed one billion inhabitants are the Americas, with a current population of around 920 million, and the Southern Hemisphere and Sub-Saharan Africa, currently each with around 860 million people. It is not known when, or if, Europe, Southeast Asia, or North America will each surpass 1 billion inhabitants.

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.^[20] By contrast, it is estimated that more than 50–60 million people lived in the combined eastern and western Roman Empire (AD 300–400).^[21]

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.^[22] The population of Europe was more than 70 million in 1340.^[23] 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.^[24] It took roughly 200 years for Europe's population to regain its 1340 level.^[25] China experienced a population decline from an estimated 123 million around 1200 to an estimated 65 million in 1393,^[26] which was presumably due to a combination of Mongol invasions and plague.^[27]

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.^[28][29] England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500.^[30] 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.^[31][32] Since being introduced by Portuguese traders in the 16th century,^[33] maize and manioc have replaced traditional African crops as that continent’s most important staple food crops.^[34] 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.^[35]

The population of the Americas in 1500 may have been between 50 and 100 million.^[36] The pre-Columbian North American population probably numbered somewhere between 2 million and 18 million.^[37] Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence.^[38] 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.^[39] Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.^[40]

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.^[41]

During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically.^[42] 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.^[43][44] Between 1700 and 1900, Europe’s population increased from about 100 million to over 400 million.^[45] Altogether, the areas of European settlement comprised 36% of the world's population in 1900.^[46]

Population growth in the West became more rapid after the introduction of compulsory vaccination and improvements in medicine and sanitation.^[47][48][49] As living conditions and health care improved during the 19th century, the United Kingdom's population doubled every fifty years.^[50] By 1801 the population of England had grown to 8.3 million, and by 1901 it had reached 30.5 million.^[51]

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.^[52] By the end of World War II in 1945, therefore, the Russian population was about 90 million fewer than it could have been otherwise.^[53]

The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941.^[54] Today, the region is home to over 1.22 billion people.^[55] The total number of inhabitants of Java increased from about five million in 1815 to more than 130 million in the early 21st century.^[56] Mexico's population grew from 13.6 million in 1900 to about 112 million in 2009.^[57] Between the 1920s and 2000s, Kenya's population grew from 2.9 million to 37 million.^[58]

Overpopulation

The scientific consensus is that the current population expansion and accompanying increase in usage of resources is linked to threats to the ecosystem.^[59][60] 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.^[61] 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 in the late 2020s.

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 organizations 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, with darker shading indicating larger populations.

The 10 countries with the largest total population:

Rank	Country / Territory	Population	Date	% of world population	Source
1	People's Republic of China[63]	1,349,040,000	February 9, 2012	19.3%	Chinese Official Population Clock
2	India	1,203,710,000	March 2011	17%	Census of India Organisation
3	United States	312,983,000	February 9, 2012	4.48%	United States Official Population Clock
4	Indonesia	238,400,000	May 2010	3.35%	SuluhNusantara Indonesia Census report
5	Brazil	195,944,000	February 9, 2012	2.8%	Brazilian Official Population Clock
6	Pakistan	178,645,000	February 9, 2012	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	2.03%	Federal State Statistics Service of Russia
10	Japan	127,380,000	June 1, 2010	1.82%	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.

Population density (people per km²) map of the world in 1994 (detailed).

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 (Taiwan)	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	16,750,000	41,526	403	[68]
9	Rwanda	9,998,000	26,338	380	[65]
10	Israel	7,697,600	20,770	371	[69]

Countries ranking highly 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	1,209,240,000	3,287,240	368	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 (Taiwan)	22,955,395	35,980	640	Declining in population[70][71]
Sri Lanka	20,238,000	65,610	309	Growing country
Netherlands	16,750,000	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.^[72] 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.^[72] The global average life expectancy is 67.07 years,^[72] with women living an average of 69 years and men approximately 65 years.^[72] 83% of the world's over-15s are considered literate.^[72]

The Han Chinese are the world's largest ethnic group, constituting over 19% of the global population.^[73] 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%).^[72] The world's largest religion is Christianity, whose adherents account for 33.35% of the global population; Islam is the second-largest religion, accounting for 22.43%, and Hinduism the third, accounting for 13.78%.^[72] In 2005, around 16% of the global population were reported to be non-religious.^[74]

Growth

Estimates of population evolution in different continents between 1950 and 2050, according to 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:

• 227.771 million in Asia.
• 92.293 million in Africa.
• 38.052 million in Latin America.
• 16.241 million in Northern America.
• 3.264 million in Europe.
• 1.955 million in Oceania.
• 383.047 million in the entire world.

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.^[75][76][77]

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),^[78] 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.^[79] 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 global variations in fertility rate per woman, according to 2005-2010 data.

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.^[80]

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.^[81] 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.^[82]

• Estimated world population figures, 10,000 BC–2000 AD.

• Estimated world population figures, 10,000 BC–2000 AD (in log y scale).

• World population figures, 1950–2000.

• Estimated global growth rates, 1950–2050.

• Estimated and projected populations of the world and its continents (except Antarctica) from 1950 to 2100. The shaded regions correspond to the range of projections by the United Nations Department of Economic and Social Affairs.

Forecasts

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,^[85] while the UN asserted that this occurred in late 2011.^[10]

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.

Growth in population by region

The table below shows historical and predicted regional population figures in millions.^{[86][87][88][89]} The availability of historical population figures varies by region.

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^[96] which represented hyperbolic growth with an infinite population in 2025.

According to Kapitsa (1997),^[97] the world population grew between 67,000 BC and 1965 according to the following formula:

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.
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