Demography

Demography is the study of the change in the size, density, distriibution and composition of human populations over time, and includes analysis of such factors as the rate of birth, death, marriage and fertility, as well as emigration and immigration. The “demographic perspective” is relating population factors (such as the size and growth of a population, or the location in urban and rural areas) to larger political, economic and social issues.

Demography has come to have a wider meaning, and is now used for all statistical descriptions of human life conditions, including illnesses, socioeconomic indicators, and other aspects of living conditions - as long as the statistics refer to the numbers of individual people who exhibit the characteristic in question.

World Population

Table 1: World population in millions, 1950-2050

1950	1960	1970	1980	1990	2000	2005	2015	2025	2050
2,519	3,024	3,697	4,442	5,280	6,086	6,465	7,219	7,905	9,076

Source: UN estimates, 2005

History of demography

The term "demography" was coined in 1855 by a Belgian, Achille Guillard in his book, Elements de statistique humaine ou demographie comparee. In his terms the study included many aspects of humans including general movement and progress (including morals) in civilized countries. He used the vital statistics of birth, marriage, sickness and death from census and registration reports."

Malthus and Malthusian models of overpopulation

see Malthusianism

Over the centuries many theorists have considered one or another aspect of population, usually to promote the policy of more people (“pronatalist.”) The early Christian tradition, however, was “antinatalist”, with the highest prestige going to priests, monks and nuns who were celibate.

In the 17th and 18th century the general belief, called "mercantilism" was that the larger the population the better for the nation. Larger population meant more farmers and more food, more people in church (and more prayers), and larger, more powerful armies for deterrence, defense and expansion. People equaled power. As Frederick the Great of Prussia put it, "The number of the people makes the wealth of states." The policy implications were clear: the state should help raise population through annexation of territory and pronatalist subsidies that encourage large families. After 1800, a rising spirit of nationalism called out for more people to make a bigger and more powerful nation.

In 1798 English writer Reverend Thomas Malthus, in "An Essay on the Principle of Population" turned the received wisdom upside down. His stunning conclusion was that more people might make it worse for everyone--that overpopulation was bad and unless proper steps were taken, disaster was inevitable. Population growth was exceedingly dangerous, he warned, for it threatened overpopulation and soon we would all starve to death. The British were taking over India at this time, and could see first-hand the horrors associated with overpopulation.

Because of the law of diminishing returns food production can only grow arithmetically: 1, 2, 3, 4, 5, etc. On the other hand, the population next year depends on the population this year, so it always expands exponentially: 2, 4, 8, 16, 32, 64, etc. In other words, population expands faster than the food supply, and eventually people will starve.

Malthus saw two ways to keep population down, "positive" and "preventive" checks. Positive checks were nasty: famine, plague and warfare. Preventive checks included voluntary actions reasonable people could take. Malthus (a clergyman) identified two types of voluntary action, the moral one of deferring marriage, and a variety of "vices" or immoral steps that included birth control, abortion, infanticide, adultery, prostitution and homosexuality.

The Malthus model was unusually powerful: it immediately generated predictions about the fate of mankind. Demography suddenly moved from an abstraction to concrete reality and attracted the attention of scholars and politicians. Economists used the model to show that the more workers there are the lower there wages will be. Charles Darwin made the struggle for food into the centerpiece of his theory of evolution of species.

Two key assumptions Malthus made were that the lure of sex was so strong that people would have babies no matter what the consequences and that technology would grow slowly or not at all. Both assumptions were wrong. Agricultural productivity has increased faster than population growth, and 200 years after Malthus the per capita food consumption in (nearly) all the world is much higher than it was then. The exception in recent decades has been sub-Sahara Africa, where Malthusian predictions of overpopulation and famine have come true.

Regarding Malthus’s first assumption, all societies have created mechanisms to control fertility (for example, by delaying marriage until the couple had enough land to feed themselves.) Everywhere family formation is a social and economic arrangement (not a sexual tryst) and is closely correlated with the supply of land, and jobs. The demographic historian John Hajnal has explored in detail the propensity in Europe in the 18th and 19th century to use delay of marriage as a population control device, tied to the shortage of farmland. In America, with no shortage of good land, the age of marriage plunged to 18 for women and 20 for men by 1800.

There are two schools of thought that follow Malthus. The "Malthusians" and "Neo-Malthusians." Both see overpopulation as a serious threat to mankind, and both agree about the linkage between unrestrained fertility and poverty. The main difference is that the Neo-Malthusians favor birth control as the main solution and the Malthusians want delayed marriage.

Demographics in Medicine and the allied health sciences

Demographic analysis is an integral part of epidemiology and in health policy. For example, currently there is a Global Burden of Disease project sponsored by the World Health Organization. (Projections of Global Mortality and Burden of Disease from 2002 to 2030 Mathers CD, Loncar D PLoS Medicine Vol. 3, No. 11, e442 doi:10.1371/journal.pmed.0030442 [1]

Mortality

• see Demography, mortality
• Infant mortality
• Life expectancy

Historical demography

see U.S. Demographic History

Demographic transition

see Demographic transition

Demographic transition theory was developed by demographers in the 1940s to provide a description and explanation of the main lines of European and American population history. The demographic transition involves three stages:

• Stage 1: In the first stage, birth rates are high and death rates are high. The population grows slowly.
• Stage 2: In the second stage modernization begins--especially industrialization (factories and railroads) and urbanization (movement off the farms). Medicine improves, as does personal hygiene and public health. This leads to a sharp fall in the death rate. Everyone lives longer, and infants are much more likely to survive. In the second stage, birth rates remain high so (with fewer deaths) the population increases rapidly.
• Stage 3: In the third stage, the death rate continues to fall and now the birth rate falls as well. Families become smaller. Instead of the rapid growth of stage two, population growth slows down; indeed, the population may start to shrink.

Bibliography

• David Coleman and Roger Schofield, eds., The State of Population Theory: Forward from Malthus (1986)

Textbooks

• Rowland, Donald T. Demographic Methods and Concepts 2003 ISBN 9780198752639
• Shryock, Henry S.; and Jacob S. Siegel. The Methods and Materials of Demography, 2 vol 1976
• Weeks, John R. Population: An Introduction to Concepts and Issues (10th ed. 2007)
• Yaukey, David and Douglas L. Anderton. Demography: The Study of Human Population. 2nd ed. 2001. Chapter 5

History of demographic theory and methods

• Susan Greenhalgh. "The Social Construction of Population Science: An Intellectual, Institutional, and Political History of Twentieth-Century Demography," Comparative Studies in Society and History, Volume 38, Issue 1 (Jan., 1996), 26-66. in JSTOR
• Hauser, Philip M., and Otis Dudley Duncan, eds. The Study of Population: An Inventory and Appraisal. 1959. sumamry of field at mid-century
• Malthus, Thomas. An Essay on the Principle of Population (1st ed 1798) (Cambridge Texts in the History of Political Thought) ed by Donald Winch 1992 ISBN 9780521429726
• Spengler, Joseph J. France Faces Depopulation (2nd ed 1979)

Historical demography

• Ansley J. Coale and Susan C. Watkins, eds. The Decline of Fertility in Europe, (1986)
• Fogel, Robert W. The Escape from Hunger and Premature Death, 1700-2100: Europe, America, and the Third World (2004)
• Reed, James. From Private Vice to Public Virtue: The Birth Control Movement and American Society Since 1830. 1978.
• Riley, James C. Rising Life Expectancy: A Global History (2001)
• Saito, Oasamu. "Historical Demography: Achievements and Prospects." Population Studies 1996 50(3): 537-553. Issn: 0032-4728 in Jstor

Demographic transition

• Davis, Kingsley. "The World Demographic Transition." Annals of the American Academy of Political and Social Science, 1945 237: 1-11. in JSTOR, classic article that introduced concept of transition
• Gillis, John R.; Louise A. Tilly; and David Levine; eds. The European Experience of Declining Fertility, 1850-1970: The Quiet Revolution. 1992.
• Szreter, Simon. "The Idea of Demographic Transition and the Study of Fertility: A Critical Intellectual History." Population and Development Review, 1993. 19:4, pp 659-701.

Current data

• CIA World Factbook, 2007. online
• Arthur Haupt and Thomas T. Kane. Population Handbook, (Population Reference Bureau: 5th ed 2004) online edition
• Wendel, Helmut, and Christopher S Wendel. Vital Statistics of the United States Births, Life Expectancy, Deaths and Selected Health Data (2006)

Journals

• Demography
• Population Studies
• Population and Development Review
• American Demographics, popular; focus on market research
• Demographic Research
• European Journal of Population
• Asia-Pacific Population Journal
• Annales De Démographie Historique
• International Migration Review

External resources

• Richard Jensen, World Population: A Guide to the WWW
• Population Index Bibliographic Searchable Database (1986-2000) from Princeton University
• Population Reference Bureau