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Population and Demographics


POPULATION AND DEMOGRAPHICS. Every place in the world has a population, human or otherwise. Big or small, old or young, growing or declining, every population changes over time and space. Human populations inhabit countries, cities, suburbs, and rural areas. In some places populations are dense, in others sparse. In some places there are more young people, in others more old people. Men dominate in some places, women in others. All of these factors constantly change over time. The study of all the statistics that describe how populations change over time and space is termed "demography." Demographic data includes, among other things, the size of a population, its density, spatial distribution, age, and gender.

Population Distribution

The distribution of the world's population is spatially uneven. Deserts contain very few people, for example, and cities contain many. Different countries, too, have very different populations. For example, consider the contrast between China and the United States. With a population of over one billion, China contains 21 percent of the world's population, whereas the United States, with a population of 283 million, has less than 5 percent. The number of people per unit area of landthe population densityalso varies among countries. In a small country like the United Kingdom (population 59 million), the density is 628 people per square mile. In comparison, a large country like the United States has a population density of 76 people per square mile, despite its larger population. Within countries, population densities vary significantly. São Paulo, Brazil, for example, has a density of around 17,000 people per square mile, whereas Amazonia has one of the lowest population densities in the world.

Since birth and death rates change over time, and since people migrate from one place to another, the world's population distribution is always changing. Countries where birth rates are greater than death rates will, in the future, gain a greater share of the world's population, as compared to countries where birth rates are similar to or less than death rates. Cross-country migration is another important factor contributing to changes in population distribution. In the early twenty-first century, some 150 million people, or 2.5 percent of the world's population, migrated either temporarily or permanently away from their countries of origin. For example, due to high rates of immigration (mainly from Latin America), the foreign-born population of the United States increased from 9.6 million in 1970 to 24.4 million in 1998. People also move within countries from rural to urban areas in a process known as urbanization. In less developed countries, for example, urbanization takes place at a rapid rate: just 18 percent of people lived in urban areas in 1950, compared to 40 percent in 2002. This number was expected to reach 56 percent by 2030.

Populations are likewise characterized by age and gender distributions. Some countries have an overwhelmingly young population, most notably those in Latin America and Africa, while others have aging populations, such as the more industrialized countries of North America and Europe. Different populations also have different sex structures. Urban societies, for example, have more males than females, a higher proportion of young adults, and a greater life expectancy.

World Population Growth

On a worldwide scale, population increases when births outnumber deaths. Although experts disagree on how exactly the world's population has grown over time, it is clear that for most of human history population growth proceeded at a very slow rate. Estimates suggest that in 40,000 B.C.E. the world's population was approximately 1.5 million, and it increased to 700 million by 1750. A falling death rate and a steady birth rate resulted in a marked increase of population to 1.6 billion in 1900. After this, in what is often termed the "population explosion," the world's population took an unprecedented move upward. In a mere sixty years the population almost doubled to 3 billion. Forty years later, in 2000, it had doubled again to over 6 billion. The reason for this growth was a rapidly falling death rate, a trend usually attributed to an increase in the world's food supply and a reduction in the rates of disease. Birth rates also fell, partially as a result of the spread of contraceptive practices, thus slowing the potential growth rate. The continuing decline of the birth rate means that the rate of population growth, though still rapid, has been slowing down. In 2002 the birth rate stood at around 1 percent, or 80 million more people per year.

Population and Food Supply

To some, the growth of the world's population has been the cause of much alarm. Even though greater food availability is part of the explanation for the ever-increasing population, at one time it seemed unthinkable that the world could support so many people. The relationship between population growth and the human food supply has, in fact, been the subject of a heated debate for hundreds of years. On one side are the so-called neo-Malthusians, named for the English clergyman Thomas Malthus. In 1798 Malthus wrote the "Essay on the Principle of Population," in which he argued that population has a tendency to increase geometrically (or more appropriately stated, exponentially), but food production increases arithmetically. Thus, population will eventually outstrip food supply, the result being many deaths from starvation. Neo-Malthusians tend not to share Malthus's analysis in its entirety; they simply share his belief that it is possible to have too many people in the world. The world, in other words, can become "overpopulated" if the number of people exceeds a carrying capacity determined by food availability and environmental resources.

Modern-day neo-Malthusianssuch as Lester R. Brown, Paul Ehrlich, Joel Cohen, Donella H. Meadows, Thomas F. Homer-Dixon, David Pimentel, and Norman Myersbelieve that population growth is a cause of famine and environmental destruction. Growth, they argue, has limits. Generally speaking, they claim that the increased demand for food arising from population growth reduces agricultural resources per person, degrades the environmental conditions in which agriculture is practiced (via soil erosion and deforestation), and exacerbates macro-environmental change (such as global warming and the depletion of the ozone layer). These changes result in a decline of food production per person and, consequently, specific populations (especially those in poor countries) experience increased death rates from malnutrition. In his book The Population Bomb, Paul Ehrlich predicted that by the 1980s the world would see massive famines as a result of food shortages stemming from overpopulation. The much-discussed 1972 Club of Rome report "Limits to Growth" concluded that the world could not support economic and population growth indefinitely. Environmentalist Lester Brown argued in numerous texts, most notably 1994's Full House, that the demand for food leads to the adoption of more intensive agriculture, which degrades environmental resources and leads to a slowdown of food output. In Environment, Scarcity, and Violence, Thomas F. Homer-Dixon maintained that environmental resources are being degraded by rapid population growth, a situation he believed would lead to conflict and insurrection, particularly in the developing world.

On the other side of the population growth debate are those who are more optimistic about the growth of the world's population. Although they possess a wide variety of views, the so-called optimists look at the situation differently. Broadly speaking, they reject the concept of overpopulation and the notion that earth has a certain carrying capacity determined by food supply and environmental limits. Rather, the optimists believe that population and resources can be manipulated by humans through ingenuity and innovation and are therefore relative.

Some of Malthus's critics are termed "cornucopians" because they believe population pressure induces technological and institutional changes that can raise food output per person. Ester Boserup argued in The Conditions for Agricultural Growth that population growth stimulates improved methods of agricultural productionvia crop rotation, fertilizers, and so onthereby increasing food supply. The economist Julian L. Simon was another prominent cornucopian. In The Ultimate Resource, he reasoned that the demand for food influences the choice of agricultural technique and leads to adoptions of innovations in market agriculture. Simon also argued that a larger population also stimulates food availability, first by expanding the pool of inventive thinkers, thereby increasing the propensity for technological change, and second by making effective food distribution systems more cost-effective. An example of technological change often put forward to disprove Malthus's thesis is the development of high-yielding varieties of crops such as rice. Bred as part of the "Green Revolution" in the 1960s, these kinds of crops arguably enabled India and other countries to feed themselves, thereby counteracting fears of calamitous starvation.

Other thinkers do not concur with Malthus simply because they believe that political and economic conditions, not population growth, determine famine and environmental destruction. An early critic of Malthus was the political economist and philosopher Karl Marx. In works like Capital (volume one), written in the 1860s, Marx accused Malthus of excusing the social conditions of his time, conditions that Marx believed were the real cause of poverty and hunger. The need to accumulate profit, Marx said, inherently means that at certain times there is a "relative surplus population," a labor force that is largely superfluous to the needs of industry. Thus, there is a class of people who periodically are unable to earn enough to afford a means of subsistence. In this way Marx asserts that it is the economic system, not population growth, that creates a population in which too many people do not have enough to eat. Economics professor and Nobel Laureate Amartya Sen has also argued that poverty and famine cannot be blamed on overpopulation. Though he accepts that population growth can place undue pressure on the environment and the lives of women, in Poverty and Famines he argues that famine results from a collapse in people's ability to purchase or otherwise acquire food, not from a shortage of food. Another critic is advocate Frances Moore Lappé and her colleagues. In World Hunger: Twelve Myths, she noted that there is no correlation between population density and hunger, and that population growth is not the root cause of hunger but is itself a consequence of social inequality. The solution, she said, is to distribute more equally the world's resources.

Trends in Population and Food Production

Throughout history, the world's food supply has grown faster than the world's population, as illustrated by the increase in the amount of cereals produced per capita. Figure 1 gives an example from recent history, indicating that cereal production has outstripped population growth since 1960 as a result of increasing yields. The area harvested per capita has actually declined.

Given this trend, it appears that neo-Malthusians have been overly pessimistic about the growing population. Most neo-Malthusians now accept that changing methods of food production have stimulated yield in a way not predicted by Malthus, but they claim the real problems have only just started. As evidence, they point to the declining rate of per-capita cereal production since 1985 (Figure 1) and the stark contrasts in food supply at the regional level (Figure 2). For example, cereal production is 0.125 metric tons per person in sub-Saharan Africa and has been declining over the past few decades. In South Asia, the per-capita rate of cereal production is higher, and the trend has been moving steadily upward. The developed world, as exemplified by the United States, produces far more cereals per capita (1.21 metric tons), but the amount has fallen since 1985.

Long-range future projections by the United Nations suggest the world's population will continue to grow, reaching 7.67 billion in 2020, and eventually 11 to 12 billion or higher by the end of the twenty-first century. Over 95 percent of growth will occur in the developing world, and the largest absolute and relative population increases will occur in Asia and Africa, respectively. Much of this growth will be in cities. The developing world's urban population is projected to double from the 1995 level of 1.7 billion to 3.4 billion in 2020.

This ever-growing population means an increased demand for food. Estimates of how much will be needed depend on the weight given to demographic factors, such as population growth, and nondemographic factors, like changing per-capita consumption. In an estimate by Tim Dyson in 1996, population growth alone will stimulate cereal demand by 728 million tons from 1990 to 2020; if nondemographic factors are accounted for, demand will be over 1 billion tons in total. Simulations by the International Food Policy Research Institute (IFPRI) predict that the world's population will demand 690 million tons more of cereal in 2020 compared with 1995. Eighty-five percent of the added demand will come from developing countries. The increasingly urbanized nature of the population means that the demand for meat will increase by 115 million tons.

The question of whether the food supply will keep up with the growing population is also the subject of a debate that has grown on local, regional, national scales. Concerns are greatest about developing countries. IFPRI predicts that food supply will not keep up with food demand in these countries. Yet IFPRI also points out that if cereal imports from the developed world doubled from 1995 levels to 2020, demands would be met. On the regional scale, sub-Saharan Africa has been the subject of significant attention. Issues such as drought and land degradation, warfare, and HIV/AIDS are all predicted to have an impact on the current trend toward declining per-capita food production. At the national scale there have been particularly marked debates about China. In Who Will Feed China? Lester R. Brown predicted that factors such as declining land availability and the degradation of water supplies will result in a shortfall of cereal production relative to population growth.

More recently, the debate has moved toward the community and household scale, the level at which people access and consume food. At this scale, however big or small the population, people are only able to eat enough food if they can access it. In order to do that, they need the means to grow food for themselves or, more likely, the money to buy it.

See also Cereal Grains and Pseudo-Cereals ; Food Politics: United States ; FAO (Food and Agriculture Organization) ; Food Supply and the Global Food Market ; Food Supply, Food Shortages ; Geography ; Government Agencies ; Political Economy .


Boserup, Ester. The Conditions for Agricultural Growth. Chicago: Aldine, 1965.

Brown, Lester R. Who Will Feed China? A Wake-up Call for a Small Planet. New York: Norton, 1995.

Brown, Lester R., and Hal Kane. Full House: Reassessing the Earth's Population Carrying Capacity. New York: Norton, 1994.

Dyson, Tim. Population and Food: Global Trends and Future Prospects. London: Routledge, 1996.

Ehrlich, Paul. The Population Bomb. New York: Ballantine Books, 1968.

Homer-Dixon, Thomas F. Environment, Scarcity, and Violence. Princeton, N.J.: Princeton University Press, 1999.

Lappé, France Moore, Joseph Collins, and Peter Rosset. World Hunger: Twelve Myths. 2d ed. New York: Grove Press, 1998.

Malthus, Thomas R. Population: The First Essay. Ann Arbor, Mich.: University of Michigan Press, 1959.

Marx, Karl. Capital, vol. 1. New York: Viking, 1977.

Meadows, Donella H., Dennis Meadows, Jorgen Rangers, and William W. Behrens III. The Limits to Growth. New York: Universe Books, 1972.

Pinstrup-Andersen, Per, Rajul Pandya-Lorch, and Mark W. Rosengrant. World Food Prospects: Critical Issues for the Early Twenty-First Century. Washington, D.C.: International Food Policy Research Institute, 1999.

Sen, Amartya. Poverty and Famines: An Essay on Entitlement and Deprivation. New York: Oxford University Press, 1981.

Simon, Julian L. The Ultimate Resource. Princeton, N.J.: Princeton University Press, 1981.

Corinna Hawkes

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