demography

The study of human populations, their growth and decline, due to changing patterns of migration, fertility and mortality , and characteristics such as the sex-ratio , dependency ratio, and age-structure. The subject is sometimes divided for further elucidation into ‘formal demography’, meaning the formal statistical analysis of population parameters and dynamics, and ‘population studies’, the wider investigation of the causes and consequences of population structures and change. It is in the latter area that many demographers have interests which overlap with those of sociologists, and in much sociological investigation demographic analysis forms an important component in the description and understanding of human societies.

The methodology consists of analysis of databases of official statistics from births, deaths, and marriage registration, and from population censuses . Demographers seek ultimately to produce population projections, that is, forecasts not only of the size of the population over coming decades, but also its changing age-structure, which can be important for social policy and labour-market policy. For example, if the dependent population (children under school-leaving age and people over retirement age) is growing relative to the population of working age which has to support it financially, there may be major implications for taxation, social insurance, and fiscal policy. If the population of working age is declining in absolute numbers, there may be a case for government policy to encourage a larger percentage (of women especially) to enter employment. Thus demographic statistics and analyses provide the essential underpinning for many other types of study. For this reason population censuses were the very first type of systematic social enquiry to be developed.

Analyses of vital statistics do, however, have their limitations. In particular, they cannot supply information on the motivations, value-systems, or aims and preferences underlying changes in the birth-rate , which is a key factor in population growth. In recent years, there have been concerted efforts to develop and carry out interview surveys on fertility orientations and behaviour. These cover issues such as the preferred number of children in a family, the effects of household income and women's employment on their fertility, attitudes to contraception and its use-all factors affecting the timing and spacing of births. The World Fertility Survey in the 1970s established standards of data collection and analysis for an important addition to the demographer's repertoire of data sources and research analyses. See also historical demography ; social demography.