Demography: the scientific study of population
In its simplest definition, demography is the scientific study of human populations. According to Landry (1945), the term demography was first used by the Belgian statistician Achille Guillard in his 1855 publication: Eléments de statistique humaine, ou démographie comparée. However, John Graunt’s Natural and Political Observations Mentioned in a Following Index, and Made Upon the Bills of Mortality, published in 1662 in London, is generally acknowledged to be the first published study in the field of demography. The book, demonstrated the usefulness of compilations of information relating to the population of London by presenting statistics on a wide range of characteristics such as employment, age and sex composition, health and environment. Graunt also published an early version of the life table which, having been further developed by Edmund Halley and Joshua Milne, led to the publication in 1840 of the first official life table by William Farr, compiler of scientific abstracts in the General Register Office for England and Wales. The life table describes the ages at which an event, death, occurs in a population. The statistical concepts of the life table remain today the fundamental elements of demographic methods. Measurement in demography applies concepts and methods from statistics and mathematics.
More generally, demographic method is concerned with describing whether and when events occur to human populations. The main events studied are childbearing, death, disease, disability, migration, entry to and exit from relationships, entry to and exit from education and employment, and entry to and exit from housing types or tenures. However, demographic methodology can be and is applied to a much wider range of events that are experienced by human populations. The study of the occurrence of several different events during a person’s lifetime is referred to as life course analysis.
Theory in demography relates to explanation of why and when events occur to people. For example, theory in demography addresses questions such as: what explains long life, what explains teenage pregnancy, what explains early school drop-out, what explains contracting a disease such as HIV/AIDS, what explains how long people live after contracting a particular disease, why do people move from rural to urban areas, why do people change their country of residence, why do people end their relationships, what explains a person’s housing tenure. Demography draws upon knowledge in other disciplines to develop its theory. The main disciplines that contribute to demographic theory are economics, sociology, anthropology, epidemiology, geography, public health, biology, ecology and environmental science. Theory in demography is established very largely through comparative analysis: comparisons across space and time and across different sub-groups of the population. In this regard, demography is inherently comparative. The methods used are primarily quantitative but the complexity of human behaviour often means that qualitative research methods are required.
Demography is concerned also with the outcomes for populations of the occurrence of ‘demographic’ events. Most basically, it is concerned with a population’s size, age structure and geographic distribution which are the outcomes of the events of birth, death and migration. One important demographic measure, the rate of population growth, is an outcome of the rates of birth, death and migration. To understand past and present rates of population growth and to predict future rates, it is necessary to have an understanding of past and present rates of birth, death and migration. More broadly, demographic events affect the composition of the population according to a wide range of characteristics: age, location, marital or relationship status, parenthood status, education, employment, occupation, industry, illness, disability, housing, ethnicity and religion. Population characteristics in turn influence a wide variety of other behaviours such as consumption, voting, and leisure.
Policy in demography is concerned with the implementation of measures that influence the course of demographic events. For example, the birth rate may be influenced through the provision of methods of contraception or through benefits provided to those having children. International movements of population are affected by national immigration policies. Public health policy has the aim of reducing rates of mortality and morbidity. Extension of education will be influenced by compulsory schooling or by means of assisting young people to stay in school. Population growth in a particularly locality will be influenced by the availability of jobs or housing.
Policy in respect of demographic events can be sensitive because it deals often with the most intimate or important areas of people’s lives. It is at this policy end of the discipline that demography becomes associated with ethics and human rights. For example, studies in demography are concerned with such issues as the provision of reproductive health rights to all members of a population, social practices that slow the reduction of maternal mortality, human trafficking and the relative rights of citizens and non-citizens.
Adolphe Landry. 1945. Traité de démographie. Paris: Payot.
Peter McDonald. 2014