World population

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Map of countries by population — China and India, the only two countries to have a population greater than one billion, together possess more than a third of the world's population. (See List of countries by population.)

Population by Continent as a percentage of World Population (1750–2005)

The world population is the total number of humans on Earth at a given time. In September, 2007, the world's population had reached over 6.7 billion. In line with population projections, this figure continues to grow at rates that were unprecedented before the 20th century, although the rate of increase has almost halved since its peak, which was reached in 1963, of 2.2 percent per year. The world's population is expected to reach over 9 billion by the year 2050.

[edit] Population figures

Below is a table with historical and predicted population figures shown in millions.^[1][2][3] The availability of historical population figures varies by region. Please see World population estimates for more figures.

* Northern America indicates the United States and Canada.

** This figure is disputed.

[edit] Rate of increase

Main article: Population growth

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

Different regions have different rates of population growth, but in the 20th century, the world saw the biggest increase in its population in human history due to medical advances and massive increase in agricultural productivity made by the Green Revolution.

In 2000, the United Nations estimated that the world's population was then growing at the rate of 1.14% (or about 75 million people) per year^[7]. According to data from the CIA's 2005–2006 World Factbooks, the world human population currently increases by 203,800 every day.^[8] The 2007 CIA factbook increased this to 211,090 people every day.

Globally, the population growth rate has been steadily declining from its peak of 2.19% in 1963, but growth remains high in the Middle East and Sub-Saharan Africa.^[9]

In some countries there is negative population growth (ie. 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.

Population growth which exceeds the carrying capacity of an area or environment results in overpopulation. Conversely, such areas may be considered "underpopulated" if the population is not large enough to maintain an economic system.

Population (est.) 10,000 BC – 2000 AD.

World population 1950–2000

Increase rate 1950–2000

[edit] Milestones

The following shows estimates of when each billion milestone was or will be met:

These numbers show that the world's population has tripled in 72 years, and doubled in 38 years up to the year 1999. Including some more 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.

[edit] Population distribution

Population density map of the world in 1994, when the world's population was at 5.6 billion; Observe the high densities along the Ganges, Yangtze and Yellow river basins, the Nile river delta, Southern Japan, Western Europe, the Indonesian island of Java, Central America (especially El Salvador, one of the world's most densely populated nations), the United States' BosWash megalopolis, and Southern California.

Asia accounts for over 60% of the world population with almost 3.8 billion people. China and India alone comprise 20% and 16% respectively. Africa follows with 840 million people, 12% of the world population. Europe's 710 million people make up 11% of the world's population. North America is home to 514 million (8%), and South America to 371 million (5.3%).

[edit] The 15 most populous nations

Population by region, 2005

The 15 states with most population

From DSW-Datareport 2006 ("Deutsche Stiftung Weltbevölkerung"):

1. China: 1.32 billion (about 20% of world population)
2. India: 1.12 billion (about 17%)
3. United States: 300 million (about 4.6%)
4. Indonesia: 225 million (about 3.5%)
5. Brazil: 186 million (about 2.8%)
6. Pakistan: 165 million (about 2.5%)
7. Bangladesh: 147 million (about 2.3%)
8. Russia: 143 million (about 2.2%)
9. Nigeria: 135 million (about 2.1%)
10. Japan: 128 million (about 2.0%)
11. Mexico: 108 million (about 1.7%)
12. Philippines: 86 million (about 1.3%)
13. Vietnam: 84 million (about 1.3%)
14. Germany: 82 million (about 1.3%)
15. Egypt: 75 million (about 1.2%)

Approximately 4.3 billion people live in these 15 countries, representing roughly two-thirds of the world's population. If added together, all nations in the European Union, with 494 million people - about 7.3% of world's population in 2006 - would be third in the list above.

[edit] Demographics of youth

According to the 2006 CIA World Factbook, around 27% of the world's population is below 15 years of age.^[10]

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 160 million-per-year raw births after 1995, the time it took to reach the next billion 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. People aged 7 through 17 make up these births, today.

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 because 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 17 to 22 make up these births, today.

[edit] Forecast of world population

See also: UN population projections

The future of world population could be significantly affected by the worldwide HIV/AIDS pandemic. In Africa, birth rates are already the highest in the world, especially in Sub-Sahara Africa. But if HIV/AIDS is controlled or even eradicated, world population could increase much faster than predicted.

In the long run, the future population growth of the world is difficult to predict. 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 itself has issued multiple projections of future world population, based on different assumptions. Over the last 10 years, the UN had consistently revised these projections downward, until the 2006 revision issued March 14, 2007 revised the 2050 mid range estimate upwards by 273 million.

Alternately, the United States Census Bureau issued a revised forecast for world population that increased its projection for the year 2050 to above 9.4 billion people (which was the UN's 1996 projection for 2050), up from 9.1 billion people. The latest Census Bureau estimates for the same upcoming years are as follows:^[11]

Other projections of population growth predict that the world's population will eventually crest, though it is uncertain exactly when or how. In some scenarios, the population will crest as early as the mid-21st century at under 9 billion, due to gradually decreasing birth rates, (the "low variant" of ^[1]), The "high variant" from the same source gives a population between 10 and 11 billion in 2050.

In other 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).

Below is a table of predicted population figures.^[1][12][13] Please see World population estimates for more figures.

* Northern America indicates the United States and Canada

[edit] Predictions based on our growing population

In 1798, Thomas Malthus incorrectly predicted that population growth would eventually outrun food supply in the middle of the 19th century, resulting in catastrophe. In 1968, Paul R. Ehrlich reignited this argument with his book The Population Bomb, which helped give the issue significant attention throughout the 1960s and 1970s. The dire predictions of Ehrlich and other neo-Malthusians were vigorously challenged by a number of economists, notably Julian Simon.

On the opposite end of the spectrum there are a number of people who argue that today's low fertility rates in Europe, North America and Australia, combined with mass immigration, will have severe negative consequences for these countries.^[14]

Child poverty has been linked to people having children before they have the means to care for them.^[15] More recently, some scholars have put forward the Doomsday argument applying Bayesian probability to world population to argue that the end of humanity will come sooner than we usually think.^[16]

It should be noted that between 1950 and 1984, as the Green Revolution transformed agriculture around the globe, world grain production increased by 250%. The energy for the Green Revolution was provided by fossil fuels in the form of fertilizers (natural gas), pesticides (oil), and hydrocarbon fueled irrigation.^[17] The peaking of world hydrocarbon production (Peak oil) may test Malthus and Ehrlich critics.^[18]

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).^[19]

[edit] Number of humans that have ever lived

Estimates of the number of human beings who have ever lived on Earth constitute an extremely large range, with low estimates around 45 billion, and the highest estimates topping out around 125 billion. Many of the more robust estimates fall into the range of 90 to 110 billion humans.

It is impossible to make anything approaching a precise count of the number of human beings who have ever lived, for the following reasons:

• The specific range of characteristics, physiological, psychological and cultural, which define a human being, continue to be a subject of intense scholarly research and debate. It is thus not possible to know just when in human evolutionary history to begin the count. Resolving these debates would require drawing a thin line between early humans and pre-humans, and in the lack of anthropological evidence, the placing of such a line is shaped by the personal interpretation of experts and remains arbitrary at best.

• Even if the scientific community reached wide consensus regarding what characteristics defined the very first human beings, it would be nearly impossible to pinpoint the exact decade, century, or millennium when they first appeared. The fossil record is simply too scarce. Only a few thousand fossils of early humans have ever been found, most no bigger than a tooth or a knucklebone. While that may sound like a large number, it is truly minuscule when you consider that these few thousand bone fragments must be used to extrapolate the population distribution of millions of early human beings spread thinly across the face of the Earth.

• Until the late 1700s, exceedingly few nations, kingdoms, or empires had ever performed a census that was considered to be anything more than a rough estimate. In many of these early attempts, the focus was not even on counting people, but merely a subset of the people for purposes of taxation or military service. Even with the advent of agencies like the United States Bureau of the Census, reliable census methods and technologies continue to evolve right into the twenty-first century. Even today, these reliable methods and technologies are not applied uniformly in all parts of the world. In short it has been less than two centuries that we have had anything that remotely resembles the robust statistical data that would be needed to perform a calculation regarding the total number of humans that have ever lived.

Considering the relatively small population in the early phases of human development, the first two factors are likely to be less significant than the third. Any such precise population count offered by any source is simply the numeric result of populations statistics, which necessarily used estimates and rough averages as their basis. While they may, if done astutely, provide us with a remote idea about the number of humans who have ever lived on the Earth, the margin of error should always be regarded as being in the billions, or even the tens of billions of people.

"Guesstimating the number of people ever born... requires selecting population sizes for different points from antiquity to the present and applying assumed birth rates to each period..."^[20]

According to one set of calculations based on 2002 data:^[20]

• The number who have ever been born is 106,456,367,669 (keeping in mind that with a error rate possibly in the tens of billions, a calculation such as this, given precision to the single digits, is for all intents and purposes arbitrary--beyond the billions level of estimation).
• The world population in mid-2002 was approximately 6,215,000,000
• The percentage of those ever born who were living in 2002 was approximately 5.8%

The claim often made in various popular sources that more than half the humans ever born are alive today, is therefore in all probability quite exaggerated.

[edit] See also

• Birth control
• Doomsday argument
• Family planning
• Green Revolution
• Life expectancy
• List of religious populations
• List of countries by population
• List of countries by population density
• List of countries by population growth rate
• List of countries by fertility rate
• List of disasters
• List of famines
• Literacy (correlated with population growth)
• Medieval demography
• One child policy
• Overpopulation
• Population control
• The Day of Six Billion
• World largest cities
• World population estimates

[edit] References

[edit] External links

• 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
• World Population Prospects. URL accessed on April 7, 2005.
• World Population Counter
• DIE OFF - a population crash resource page
• 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.
• Population Reference Bureau www.prb.org - News and issues related to population.
• (French) World Population Clock (2005). WorldPopClock.com - World population clock.
• Population Counter. Real time counter..
• Population Information on population, population growth, population problems, population statistics, and population figures.
• World maps, including maps of population from Year 1 to Year 2300
• Live World Population
• World Population Counter
• World Population Counter
• World Population from the US Census Bureau in an interactive Excel dashboard