Table

World Population, 1900, 1950, and 2000, and Projections for 2050

World World World

2050 Qrowth Growth Growth

1900 1950 2000 Estimate 1900-1950 1950-2000 2000-2050

World 1,650* 2,519 6,057 9,322 100 100 100

Developed Countries 543 814 1,191 1,181 31 11 0

Developing Countires 1,107 1,706 4,865 8,141 69 89 100

*All populations given in millions.

Sources: 1900, author's estimates. 1950, 2000, and 2050 United Nations Population Division. 2000 World Population Prospects, The 2000 Revision. New York: United Nations.

planning, such as abstinence and withdrawal, become more widely practiced, and reduced family size follows. In many developed countries, this process was well underway in the nineteenth century. At the same time, advances in medicine and public health began to lengthen lives. The end of the demographic transition features low birth and death rates, and, if the average number of children declines to about two, population growth will eventually cease.

It is often pointed out that the demographic transition actually occurred at different times and in different ways from country to country, but the overall pattern has proven reasonably valid. That process is, of course, essentially complete in the developed countries, and, in fact, the transition had the surprise ending of extremely low fertility in much of the developed world; decline seems now to be the end of the story.

The major turning point in modern world population history came at about the middle of the twentieth century, when the mortality revolution spread to the developing countries. At that time, demographic rates in most developing countries still had the earmarks of the prein-dustrial condition. The level of infant mortality meant that 20 percent of newborns died in the first year of life, and a roughly equal proportion died before their fifth birthday. But medical advances that had taken centuries to emerge in the developed countries and were themselves still somewhat new spread rapidly throughout the world. The outcome was a level of mortality that dropped with unheard of speed throughout the developing world. At the time it could not be known, but the developing countries had begun their own demographic transition—but in a rather different way.

The decline in mortality from disease was so swift that fertility largely remained where it was, typically an average of six or seven children per woman. Developing country soci eties were still primarily agricultural, and the preference or perceived need for a large family remained. The result was a population growth rate that rose to a level that had never before been seen. The population growth rate rose to 2.5 percent per year, a rate that would double a population's size in less than thirty years.

The new population "explosion" gave rise to renewed fears of Malthusian principles. In his 1798 treatise, An Essay on the Principle of Population, the British clergyman and economist Robert Thomas Malthus had argued that, while population grew geometrically (that is, doubling in size during a fixed time period and increasing by twice as much in the next time period), the food supply grew by a fixed amount. The specter of starvation in the developing countries seemed quite real and, for a time, quite possibly was. Early population projections were quite pessimistic.

Several factors intervened to forestall a complete Malthusian calamity. For one, the Green Revolution greatly increased food production in many countries. But the second factor was just as important: in the 1970s, a growing number of developing countries determined that rapid population growth simply could not be sustained indefinitely if they were to make significant progress in raising overall health and living conditions. Population policies to slow population growth and provide family planning services spread rather quickly (India was the first country to adopt a population policy in 1952).

By 2000, an extraordinarily rapid fertility transition was underway in the developing world—although not in all countries. Fertility declined from about six children per woman in 1950 to slightly less than three. This is the second part of the developing countries' demographic transition. It differs, however, from that of the developed countries by its speed.

Much of the decline in both fertility and mortality has taken place in countries that remain largely agricultural and with relatively low levels of education. And it has done so in a matter of decades, not centuries.

The dramatic decline in developing country birth rates has been hailed by some observers as the end of Malthusian concern, but demographic arithmetic contradicts that point of view. The process of demographic transition is only partially complete. Given the still young age structure of developing countries, tremendous potential population growth remains. Fertility decline has barely begun in Africa and other countries, particularly in the Middle East, and it has stalled in others. Progress toward the two-child family remains very much in doubt. The projected population for 2050 given in the table above assumes that fertility decline will, in fact, be smoothly uninterrupted and be largely complete in many countries well before 2050. If that is not the case, future population may be very much larger than shown.

It is certainly true that demographic history has not been without it surprises, such as the postwar "baby boom" in the United States and the unexpected appearance of HIV/AIDS. But we can, at this stage, make at least one prediction for the population history of this new century. It will see a continued expansion of population in developing countries that may well be larger than that of the last. Whatever the outcome, we can be certain that future generations will look back on these as the "population centuries."

See also: Agriculture and Biodiversity Loss: Genetic Engineering and the Second Agricultural Revolution; Agriculture, Origin of; Homo Sapiens; Human Evolution; Population, Human, Curbs to Growth; Urbanization

Bibliography

Carr-Saunders, A. M. 1964. World Population: Past

Growth and Present Trends. London: Frank Cass; Cohen, Joel. 1995. How Many People Can the Earth Support? New York: W. W. Norton; Haub, Carl, and Diana Cornelius. 2001. 2001 World Population Data Sheet. Washington, DC: Population Reference Bureau; Heer, David M. 1975. Society and Population, 2d ed. Englewood Cliffs, NJ: Prentice Hall; Livi-Bacci, Massimo. 1992. A Concise History of World Population. Translated by Carl Ipsen. Cambridge, MA: Blackwell; McEvedy, Colin, and Richard Jones. 1976. Atlas of World Population History. New York: Viking/Penguin; UN Population Division. 2001. World Population Prospects: The 2000 Revision. New York: United Nations; Wrigley, E. A. 1969. Population and History. New York: McGraw-Hill.

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