The world population is the total number of living humans on Earth at a given time. As of 1 December 2009, the Earth's population is estimated by the United States Census Bureau to be 6.8 billion. The world population has been growing continuously since the end of the Black Death around 1400. 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 about 9 billion by the year 2040.
Population figures
Further information: World population estimatesA 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 over 55 million people lived in the combined eastern and western Roman Empire (AD 300–400). The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 700s. The population of the world was more than 440 million in 1340. 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. It took roughly 200 years for Europe's population to regain its 1340 level.
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. England's population reached an estimated 5.6 million in 1650, up from an estimated 2.6 million in 1500. 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. Since being introduced by Portuguese traders in the 16th century, maize and manioc have replaced traditional African crops as the continent’s most important staple food crops. 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."
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. Over the centuries, the Europeans had developed high degrees of immunity to these diseases, while the indigenous peoples had no such immunity.
During the Agricultural and Industrial Revolutions, the life expectancy of children increased dramatically. 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. Europe’s population doubled during the 18th century, from roughly 100 million to almost 200 million, and doubled again during the 19th century. The population growth became more rapid after the introduction of compulsory vaccination and improvements in medicine and sanitation. As living conditions and health care improved during the 19th century, Britain's population doubled every 50 years. By 1801 the population of England had grown to 8.3 million, and by 1901 had grown to 30.5 million.
The population of the Indian subcontinent, which stood at about 125 million in 1750, had reached 389 million by 1941. The region is currently home to 1.5 billion people. The total number of inhabitants of Java increased from about 5 million in 1815 to more than 130 million in the early 21st century. Mexico's population has grown from 13.6 million in 1900 to about 112 million in 2009.
Below is a table with historical and predicted population figures shown in millions.
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.
Rate of increase
Main article: Population growthDifferent 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.
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, 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. The CIA Factbook increased this to 211,090 people every day in 2007, and again to 220,980 people every day in 2009.
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.
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. 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.
Models
Hoerner (1975) proposed the following formula:
where
- N is current population
- T is the current year
- C = 2·10 11
- T 0 = 2025
but this represents hyperbolic growth with an infinite population in 2025.
According to Kapitsa (1997), 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)·10 11
- T 0 = 2007±1
- τ = 42±1
The transition from hyperboles to slower rates of growth is called demographic transition .
Milestones
There is currently no estimation on the exact day 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 U.S. Census Bureau places them around July 1959, and April 1974. The United Nations did determine, and celebrate, the "Day of 5 billion" (July 11, 1987), and the "Day of 6 billion" (October 12, 1999). The U.S. Census bureau, International Programs division, currently estimated that the world reached 6 billion on April 21, 1999 (several months earlier than the official UN day). The "Day of 7 billion" has been targeted by the Census Bureau to be in July 2012.
Years for population to
International Programs
World POPClock Projection . According to the International Programs Center, U.S. Census Bureau, the total population of the World, projected to 11/28/09 at 11:29 UTC (EST+5) is
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