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The world population is the total number of living humans on Earth at a given time. As of November 2008, the world's population is estimated to be about 6.7 billion (6,700,000,000). In line with population projections, this figure continues to grow at rates that were unprecedented before the 20th century, although the rate of growth has almost halved since its peak of 2.2% per year, which was reached in 1963. The world's population, on its current growth trajectory, is expected to reach nearly 9 billion by the year 2042.¹² Please see World population estimates for more figures.

Population figures

It is estimated that over 50 million people lived in the combined eastern and western Roman Empire (300–400 AD).³

Below is a table with historical and predicted population figures shown in millions.⁴⁵⁶ The availability of historical population figures varies by region.

Rate of increase

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:

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.¹²¹³

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,¹⁴ down from a peak of 86 million per year in 1987. 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.¹⁵ The 2007 CIA factbook increased this to 211,090 people every day.

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.

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; however, many who do not view overpopulation as a serious problem fail to consider the sustainability of economic systems, the environmental degradation caused, and the ecological footprint of the existing population.

The United Nations states that population growth is rapidly declining due to the demographic transition. The world population is expected to peak at 9.22 billion in 2075. [2]

Milestones

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.

Distribution

Population density map of the world in 1994, when the world's population was at 5600 million; Observe the high densities in the Indo-Gangetic and North China Plains, the Sichuan Basin, the Nile river delta, Southern Japan, Western Europe, the Indonesian island of Java, Central America (especially El Salvador, the Americas' most densely populated nation), and the United States' BosWash megalopolis.

Asia accounts for over 60% of the world population with almost 3800 million people. The People's Republic of China and India alone comprise 20% and 17% 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%), South America to 371 million (5.3%), and Australia 21 million.

The 15 most populous nations

Approximately 4300 million 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 below.

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. For comparison 6.06% of the planet's population is of full or partial Spanish ancestry, and on a wider scale 14.2% of earth's population is of Sub-Saharan descent (those identifying as 'Black')^{citation needed}.

Demographics of youth

According to the 2006 CIA World Factbook, around 27% of the world's population is below 15 years of age.¹⁸

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 10⁹ reached its fastest pace (only 12 years), as world population reached 6000 million 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.

Forecast

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.

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. A new US Census Bureau revision from June 18, 2008 has increased its projections further, to beyond 9.5 billion in 2050.

Other projections are that the world's population will eventually crest, though it is uncertain when or how. In some scenarios, it will crest as early as around 2050 at under 9 billion, or 10 to 11 billion, due to gradually decreasing birth rates.⁴).

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 and food security).

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.²¹

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).³⁶

Child poverty has been linked to people having children before they have the means to care for them.³⁸ Some scholars have put forward the Doomsday argument applying Bayesian probability to world population to argue that the end of humanity will come within 9,000 years.³⁹

Number of humans who have ever lived

In the 1970s it was popular to believe that 75% of all the people who had ever lived were alive in the 1970s, which would have put the total number of people to ever live as of the 1970s, as less than the current number of people alive today. This view was eventually debunked as a myth⁴⁰. 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.⁴¹⁴² 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".⁴² 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 2002.⁴¹

Other estimates of the total number of people who have ever lived range approximately from 45 billion to 125 billion, with the more robust of these falling in the 90–110 billion range.^{citation needed}. It is difficult to estimate for the following reasons:^{citation needed}

Further resources

References

^ World Population Clock - Worldometers
^ International Data Base (IDB) - World Population
^ Population estimates of the Roman Empire, Dr. Kenneth W. Harl
^ ^a ^b ^c World population prospects: the 2004 revision population database
^ The World at un.org
^ ^a ^b Population Growth over Human History
^ UN report 2004 data
^ Humans lived in tiny, separate bands for 100,000 years
^ ^a ^b ^c an average of figures from different sources as listed at the US Census Bureau's Historical Estimates of World Population; see also *Kremer, Michael. 1993. "Population Growth and Technological Change: One Million B.C. to 1990," The Quarterly Journal of Economics 108(3): 681-716.
^ Bishop Ussher places creation of Adam and Eve; world population two.
^ The range of figures from different sources as listed at the US Census Bureau's Historical Estimates of World Population put the population at 1 AD between 170 million to 400 million.
^ The limits of a Green Revolution?
^ The Real Green Revolution
^ census.gov
^ Current world population (ranked)
^ Ron Nielsen, The little green handbook, Picador, New York (2006) ISBN 0-312-42581-3
^ From DSW-Datareport 2006 ("Deutsche Stiftung Weltbevölkerung")
^ Age structure of the world – 2006 CIA World Factbook
^ U.S. Census Bureau - International Data Base (IDB)
^ The World at Six Billion
^ BBC NEWS | World | Assessing the global food crisis
^ Eating Fossil Fuels |EnergyBulletin.net
^ Peak Oil: the threat to our food security
^ Peak Oil And Famine:Four Billion Deaths
^ 2008: The year of global food crisis
^ The global grain bubble
^ Food crisis will take hold before climate change, warns chief scientist
^ Global food crisis looms as climate change and fuel shortages bite
^ Experts: Global Food Shortages Could ‘Continue for Decades'
^ Has Urbanization Caused a Loss to Agricultural Land?
^ The World's Growing Food-Price Crisis
^ The cost of food: Facts and figures
^ Riots and hunger feared as demand for grain sends food costs soaring
^ Already we have riots, hoarding, panic: the sign of things to come?
^ Feed the world? We are fighting a losing battle, UN admits
^ The limits of a Green Revolution?
^ The Death of the West: How Dying Populations and Immigrant Invasions Imperil Our Country and Civilization (ISBN 0-312-30259-3), by Patrick Buchanan, The Empty Cradle: How Falling Birthrates Threaten World Prosperity (ISBN 0-465-05050-6), by Longman, and Fewer: How the New Demography of Depopulation Will Shape Our Future (ISBN 1-56663-606-X), by Wattenberg
^ Population bomb still ticking away - 20 Mar 2007 - NZ Herald
^ DIE OFF - a population crash resource page
^ Population Reference Bureau
^ ^a ^b Curtin, Ciara (2007-03-01), "Fact or Fiction?: Living People Outnumber the Dead", Scientific American (Scientific American, Inc.) 297 (3): 126, September 2007, http://www.sciam.com/article.cfm?id=fact-or-fiction-living-outnumber-dead, retrieved on 4 August 2008 Note: text of paper publication slightly different than text of on-line publication
^ ^a ^b Haub, Carl (November/December 2002), "How Many People Have Ever Lived on Earth?", Population Today (Population Reference Bureau) 30 (8): 3–4, http://www.prb.org/pdf/PT_novdec02.pdf, retrieved on 4 August 2008
^ [1], University of Sheffield 'Worldmapper' site
^ Global Statistics interactive atlas, www.GeoHive.com

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