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World population
Map of countries by population—China and India, the only two countries to have a population greater than 1 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 living humans on Earth at a given time. As of September 2008, the world's population is estimated to be just over 6.721 billion. 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.[1][2]
Population figuresCensuses taken between 300–400 AD showed over 50 million people living in the combined eastern and western Roman empire.(citation Dr. Kenneth W. Harl, tulane.edu) Below is a table with historical and predicted population figures shown in millions.[3][4][5] The availability of historical population figures varies by region. (Note: These projections here are not kept up to date.) Please see World population estimates for more figures.
* Northern America indicates the northern countries and territories of North America: Canada, the United States, Greenland, Bermuda, and St. Pierre and Miquelon. This should not be confused with the term "North America" which typically includes Mexico. The United Nations data includes Mexico as part of Latin America. ** This figure is disputed. 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:
In the unusual case of 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 growing at the rate of 1.14% (or about 75 million people) per year,[10] 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.[11] 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.[12] 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. http://www.un.org/esa/population/publications/longrange2/WorldPop2300final.pdf <gallery> Image:Population curve.svg|Population (est.) 10,000 BC – 2000 AD. Image:World population curve - log y scale.png|Population (est.) in log y scale Image:World population history.svg|World population 1950?2000 Image:World population increase history.svg|Increase rate 1950?2000 </gallery> 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. The 15 most populous nations
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.
Population by region, 2007 EthnicityThe world is made up of hundreds of thousands of ethnic groups, and due to mass migration across the planet over millennia, it is impossible to tell how many people belonging to a certain ethnic group inhabit the earth. 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'). Demographics of youthAccording to the 2006 CIA World Factbook, around 27% of the world's population is below 15 years of age.[14] 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.[3]). 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 growthIn 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.[17] From 1950 to 1984, as the Green Revolution transformed agriculture around the 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.[18] The peaking of world hydrocarbon production (Peak oil) may test Malthus and Ehrlich critics.[19][20] As of May 2008, the price of grain has been pushed up by increased farming for use in biofuels,[21] world oil prices at over $140 per barrel,[22] global population growth,[23] climate change,[24] loss of agricultural land to residential and industrial development,[25][26] and growing consumer demand in China and India[27][28] Food riots have recently occurred in many countries across the world.[29][30][31] 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).[32] On the opposite end of the spectrum, a number of people argue that today's low fertility rates in Europe, North America, Japan and Australia, combined with mass immigration, will have severe negative consequences for these countries.[33] Child poverty has been linked to people having children before they have the means to care for them.[34] 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.[35] Number of humans who have ever livedAn 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.[36][37] 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".[37] 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.[36] 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.. It is difficult to estimate for the following reasons:
Further resources
ReferencesSee also
External links
ca:Població mundial de:Weltbevölkerung es:Población humana fa:????? ???? fr:Population mondiale ko:?? ?? id:Populasi dunia lt:Pasaulio gyventojai mr:?????? ????????? mn:??????? ??? ?? nl:Wereldbevolking ja:???? pl:Ludno?? ?wiata pt:População mundial ru:??????? ????????? ????? sh:Svjetsko stanovni?tvo fi:Maailman väkiluku tr:Dünya nüfusu zh:???? Source: Wikipedia | The above article is available under the GNU FDL. | Edit this article
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