Population density (people per km²) by country, 2006

World population 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 Earth at a given time. As of 28 December 2009, the Earth's population is estimated by the United States Census Bureau to be 6,792,800,000.^[1] The world population has been growing continuously since the end of the Black Death around 1400.^[2] The fastest rates of world population growth (above 1.8%) were seen briefly during the 1950s then for a longer period during the 1960s and 1970s (see graph). According to population projections, world population will continue to grow until at least 2050. The 2008 rate of growth has almost halved since its peak of 2.2% per year, which was reached in 1963. World births have levelled off at about 134 million per year, since their peak at 163 million in the late 1990s, and are expected to remain constant. However, deaths are only around 57 million per year, and are expected to increase to 90 million by the year 2050. Because births outnumber deaths, the world's population is expected to reach 9 billion in 2040.^[3][4]

[edit] Population figures

A dramatic population bottleneck is theorized for the period around 70,000 BC (see Toba catastrophe theory). After this time and until the development of agriculture, 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. It is estimated that more than 55 million people lived in the combined eastern and western Roman Empire (AD 300–400).^[5] The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 700s.^[6] The population of Europe was more than 70 million in 1340.^[7] 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.^[8] It took roughly 200 years for Europe's population to regain its 1340 level.^[9]

At the founding of the Ming dynasty in 1368, China's population was reported to be close to 60 million, and toward the end of the dynasty in 1644 it might have approached 150 million.^[10][11] England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500.^[12] New crops that had come to Asia and Europe from the Americas via the Spanish colonizers in the 16th century contributed to the population growth.^[13][14] Since being introduced by Portuguese traders in the 16th century,^[15] maize and manioc have replaced traditional African crops as the continent’s most important staple food crops.^[16] Alfred W. Crosby speculated that increased production of maize, manioc, and other American crops "enabled the slave traders drew many, perhaps most, of their cargoes from the rain forest areas, precisely those areas where American crops enabled heavier settlement than before."^[17]

Scholars estimate that between 900,000 and 18 million people inhabited North America north of present-day Mexico at the time of European contact.^[18]

Urban areas with at least one million inhabitants in 2006. In 1800, only 3% of the world's population lived in cities, a figure that has risen to 47% by the end of the twentieth century.

Encounters between European explorers and populations in the rest of the world often introduced local epidemics of extraordinary virulence. Archaeological evidence indicates that the death of 90 to 95% of the Native American population of the New World was caused by Old World diseases such as smallpox, measles, and influenza.^[19] Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.^[20]

During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically.^[21] 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.^[22][23] Europe’s population doubled during the 18th century, from roughly 100 million to almost 200 million, and doubled again during the 19th century.^[24] The population growth became more rapid after the introduction of compulsory vaccination and improvements in medicine and sanitation.^[25][26][27] As living conditions and health care improved during the 19th century, Britain's population doubled every 50 years.^[28] By 1801 the population of England had grown to 8.3 million, and by 1901 had grown to 30.5 million.^[29]

The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941.^[30] The region is currently home to 1.5 billion people.^[31] The total number of inhabitants of Java increased from about 5 million in 1815 to more than 130 million in the early 21st century.^[32] Mexico's population has grown from 13.6 million in 1900 to about 112 million in 2009.^[33] In 80 years, Kenya's population has grown from 2.9 million to 37 million.^[34]

Below is a table with historical and predicted population figures shown in millions.^{[35][36][37][38]}
The availability of historical population figures varies by region.

* Northern America comprises the northern countries and territories of North America: Canada, the United States, Greenland, Bermuda, and St. Pierre and Miquelon. Latin America comprises Middle America (Mexico, the nations of Central America, and the Caribbean) and South America.

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

[edit] Rate of increase

Population evolution in different continents. The vertical axis is logarithmic and is millions of people.

Different regions have different rates of population growth. According to the above table, the growth in population of the different regions from 2000 to 2005 was:

237.771 million in Asia

92.293 million in Africa

38.052 million in Latin America

16.241 million in Northern America

1.955 million in Oceania

-3.264 million in Europe

383.047 million in the whole world

In the 20th century, the world saw the biggest increase in its population in human history due to lessening of the mortality rate in many countries due to medical advances and massive increase in agricultural productivity attributed to the Green Revolution.^[43][44][45]

In 2000, the United Nations estimated that the world's population was growing at the rate of 1.14% (or about 75 million people) per year,^[46] down from a peak of 88 million per year in 1989. In the last few centuries, the number of people living on Earth has increased many times over. By the year 2000, there were 10 times as many people on Earth as there were 300 years ago. According to data from the CIA's 2005–2006 World Factbooks, the world human population increased by 203,800 every day.^[47] The CIA Factbook increased this to 211,090 people every day in 2007, and again to 220,980 people every day in 2009.

Map of countries and territories by fertility rate

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.^[48]

In some countries there is negative population growth (i.e. net decrease in population over time), especially in Central and Eastern Europe (mainly due to low fertility rates) and Southern Africa (due to the high number of HIV-related deaths). Within the next decade, 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 demographic transition. If this trend continues, the rate of growth may diminish to zero, concurrent with a world population plateau of 9.2 billion, in 2050.^[49] However, this is only one of many estimates published by the UN. In 2009, UN projections for 2050 range from about 8 billion to 10.5 billion.^[50]

Population (est.) 10,000 BC–AD 2000.

Population (est.) 10,000 BC–AD 2000 in log y scale

World population 1950–2000

Increase rate 1950–2000

[edit] Models

Hoerner (1975) proposed the following formula:^[51]

where

• N is current population
• T is the current year
• C = 2·10¹¹
• T₀ = 2025

but this represents hyperbolic growth with an infinite population in 2025.

According to Kapitsa (1997)^[52], the population grew between 67000 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 called demographic transition.

[edit] Milestones

World population milestones (in billions, estimated).

The population of the world reached 1 billion in 1804, 2 billion in 1927, 3 billion in 1960, 4 billion in 1974, 5 billion in 1987, and 6 billion in 1999. The population of the world is projected to reach 7 billion in 2012, 8 billion in 2025, and 9 billion in 2040.

There is currently no estimation on the exact day or month the world's population surpassed both the 1 and 2 billion marks. The day of 3 and 4 billion were not officially celebrated, 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" (11 July 1987), and the "Day of 6 Billion" (12 October 1999). The International Programs division of the United States Census Bureau currently estimated that the world reached 6 billion on 21 April 1999 (several months earlier than the official United Nations day). The "Day of 7 Billion" has been targeted by the United States Census Bureau to be in July 2012.^[53]

[edit] Years for 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.^[54]

Years for Population to Double

[edit] Distribution by region

Population density map of the world in 1994, when the world's population was 5.6 billion; Observe the high densities in the Indo-Gangetic and North China plains, the Sichuan Basin, the Nile river delta, Southern Japan, Western Europe, Java, and the Boston-Washington corridor.

Asia accounts for over 60% of the world population with almost 3.8 billion people. China and India together have about 40 percent of the world's population. Africa follows with 840 million people, 12% of the world's population. Europe's 710 million people make up 11% of the world's population. North America is home to 514 million (8%), South America to 371 million (5.3%), and Australia to 21 million (0.3%).

[edit] Most populous nations

Map of countries by population

Population by region, 2007

The 16 countries with the largest total population:

Rank	Country / Territory	Population	Date	% of world population	Source
1	China (excluding Hong Kong and Macau)	1,334,018,022	02009-11-09November 9, 2009	19.67%	Chinese Population Clock[55]
2	India	1,198,003,000		17.64%	UN estimate
3	United States	307,896,665	02009-11-09 November 9, 2009	4.52%	Official USA Population clock
4	Indonesia	230,729,491	02009-07-21 July 21, 2009	3.41%	Indonesian Population clock
5	Brazil	192,012,993	02009-11-09 November 9, 2009	2.83%	Brazilian Population clock
6	Pakistan	167,905,500	02009-11-09 November 9, 2009	2.48%	Pakistani Population clock
7	Bangladesh	157,813,124	02009-11-09 November 9, 2009	2.32%	Private Bangladeshi Population clock
8	Nigeria	148,235,170		2.19%	UN estimate
9	Russia	141,889,164	02009-11-09 November 9, 2009	2.09%	Russian Population Clock
10	Japan	127,614,000	02009-07-21 July 21, 2009	1.88%	Japanese Statistics Bureau
11	Mexico	111,809,963	02009-11-09 November 9, 2009	1.64%	Private Mexican Population Clock
12	Philippines	94,377,140	02009-07-21 July 21, 2009	1.39%	Private Filipino Population Clock
13	Vietnam	87,017,453	02009-07-21 July 21, 2009	1.28%	Private Vietnamese Population Clock
14	Germany	82,060,000	02008-12 December 2008	1.21%	Federal Statistical Office of Germany
15	Ethiopia	79,221,000	02008-07 July 2008	1.17%	Ethiopia Central Statistics Agency
16	Egypt	77,439,137	02009-11-09 November 9, 2009	1.14%	Egyptian Population Clock

Approximately 4.51 billion people live in these 16 countries, representing roughly two-thirds (66.7%) of the world's population as of February 2009.

The 10 most densely populated countries

Rank	Country	Population	Area (km2)	Density (Pop per km2)	Notes
1	Monaco	32,719	1.95	16,779	[56]
2	Singapore	4,620,657	707.1	6,535
3	Vatican City	824	0.44	1,873	[57]
4	Maldives	385,375	298	1,293
5	Malta	404,032	316	1,279
6	Bahrain	723,967	665	1,089	[58]
7	Bangladesh	157,813,124	147,570	1,069	[59]
8	Palestinian territories	4,223,760	6,020	702
9	Nauru	13,918	21	663
10	Taiwan	22,955,395	36,190	634	[57]

[edit] Ethnicity

The world is made up of thousands of ethnic groups. The single largest ethnic group on the planet by far is Han Chinese, which represents 19.73% of the global population.^{[citation needed]}

[edit] Demographics of youth

According to the 2006 CIA World Factbook, around 27% of the world's population is below 15 years of age.^[60]

Before adding mortality rates, the 1990s saw the greatest number of raw births worldwide, especially in the years after 1995, despite the fact that the birth rate was not as high as in the 1960s. In fact, because of the 163 million-per-year raw births after 1995, the time it took to reach the next 10⁹ reached its fastest pace (only 12 years), as world population reached 6 billion people in 1999, when at the beginning of the decade, the reaching was designated for the year 2000, by most demographers. These people aged 9 through 18 make up these births today, and are either from the late Generation Y group, or are in the Generation Z group.

1985–1990 marked the period with the fastest yearly population change in world history. Even though the early 1960s had a greater growth rate than in the mid and late 1980s, the population change hovered around 83 million people in the five-year period, with an all-time growth change of nearly 88 million in 1990. The reason is that the world's population was greater in the mid- and late-1980s (around 5 billion) than in the early 1960s (around 3 billion), which meant that the growth rate in the 1980s was no factor on the dramatic population change. People aged 19 to 24 make up these births today, and are a part of Generation Y.

[edit] Forecast

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 7 billion in July 2012.^[63]

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 10 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).

[edit] Predictions based on population growth

In 1798 Thomas Malthus incorrectly predicted that population growth would outrun 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 kept pace with population growth, but Malthusians point out the green revolution relies heavily on petroleum-based fertilizers, and that many crops have become so genetically uniform that a crop failure would be very widespread. Food prices in the early 21st century are rising sharply on a global scale, and causing serious malnutrition to spread widely.^[65]

From 1950 to 1984, as the Green Revolution transformed agriculture around the world, grain production increased by over 250%.^[66] The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon-fueled irrigation.^[67] The peaking of world oil production (Peak oil) may test Malthus and Ehrlich critics.^[68][69] As of May 2008, the price of grain has been pushed up by increased farming for use in biofuels,^[70] world oil prices at over $140 per barrel ($880/m³),^[71] global population growth,^[72] climate change,^[73] loss of agricultural land to residential and industrial development,^[74][75] and growing consumer demand in China and India.^[76][77] Food riots have recently occurred in many countries across the world.^[78][79][80]

Growing populations, falling energy sources and food shortages will create the "perfect storm" by 2030, the UK government chief scientist has warned. He said food reserves are at a 50-year low but the world requires 50% more energy, food and water by 2030.^[81][82] The world will have to produce 70% more food by 2050 to feed a projected extra 2.3 billion people and as incomes rise, the United Nations' Food and Agriculture Organisation (FAO) said.^[83]

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).^[84]

[edit] Number of humans who have ever lived

In the 1970s it was a popular belief that 75% of all the people who had ever lived were alive in the 1970s, which would have put the total number of people who ever lived as of the 1970s as less than the current number of people alive today. This view was eventually debunked as a myth.^[85] A more recent estimate of the total number of people who have ever lived was prepared by Carl Haub of the Population Reference Bureau in 1995 and subsequently updated in 2002; the updated figure was approximately 106 billion.^[86][87] Haub characterized this figure as an estimate which required "selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period".^[87] 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.^[86]

Other estimates of the total number of people who have ever lived range approximately from 100 billion to 115 billion. It is difficult to estimate for the following reasons:^{[citation needed]}

• The set of specific characteristics which define a human and distinguish early Homo sapiens from earlier or related species continues to be a subject of intense research and debate. It is thus not possible to know when to begin the count, nor which hominids to include. See in this regard also Sorites paradox. Even if the scientific community reached wide 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 because the fossil record is simply too sparse. Only a few thousand fossils of early humans have been found, most no bigger than a tooth or a knucklebone. These bone fragments are used to extrapolate the population distribution of millions of early human beings spread across the continents. However, the limited size of population in early times compared to its recent 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 nations, kingdoms, or empires 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.^[88] 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 item for the estimation is life expectancy. Using a figure of 20 years and the population estimates above, one can compute about 58 billion. Using a figure of 40 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 10 years for most of human history"^[87] His estimates for infant mortality suggest that around 40% of those who have ever lived did not survive beyond the age of 1 year.

[edit] See also

[edit] Further resources

• There is a map that is rescaled in order to display every country according to its population size. It is available at the University of Sheffield Worldmapper.^[89]
• Population patterns and trends can be explored on the GeoHive interactive world atlas.^[90]

[edit] References

[edit] External links

• World Population Prospects (United Nations Population Division).
• World population statistics presented in a treemap interface
• Year-by-Year World Population Estimates: 10,000 BC to AD 2007.
• Optimum Population Trust
• State of World Population 2007 report 27 June, 2007 - United Nations Population Fund
• World Population Day United Nations: 11 July
• The Day of 6 Billion official homepage
• Trend of growth rate with total global population
• The World in Balance Transcript of two-part PBS' Nova on World Population
• BBC (1999). UN chief welcomes six billionth baby. URL accessed on March 7, 2005.
• Central Intelligence Agency (2004). CIA The World Factbook 2004. URL accessed on February 13, 2005.
• United Nations (2001). United Nations Population Information Network. URL accessed on February 13, 2005.
• United States Census Bureau (2004). Historical Estimates of World Population. URL accessed on February 13, 2005.
• PopulationData.net (2005). PopulationData.net - Information and maps about populations around the world.
• GeoHive GeoHive.com - World Statistics including population and future predictions.
• Population Reference Bureau www.prb.org - News and issues related to population.
• World maps, including maps of population from Year 1 to Year 2300
• Berlin Institute for Population and Development [2]
• World Population from the US Census Bureau in an interactive Excel dashboard

Population clocks

• Population Counter
• World Population
• World Population Counter
• Live World Population
• (French) World Population Clock (2005). WorldPopClock.com - World population clock.