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What is demography?

Blog • Sociology • Heather Joshi FBA

You may have heard of ‘demographics’ in the context of target groups for marketing companies or political campaigns. You may also have heard of demography as the scientific study of the human population. It underpins and interacts with many other fields concerned with history, geography, biology, ecology, economics, statistics, epidemiology and social policy.

Babies in their cots at the Duchess of York's Hospital, Manchester. 1939. Photo by Fox Photos / Getty Images.Globally, population growth has been a concern since Thomas Malthus’s 1798 Essay of the Principle of Population questioned whether the Earth had the capacity to feed an ever-growing multitude and how numbers could stabilise. The population of the planet is still growing, but more slowly, it is expected to pass eight billion in the 2020s. Today’s picture varies across continents and indeed particular regions. In some places the population size is stable or even declining, in others, like Sub-Saharan Africa, high birth rates and better child survival lead to a population that is growing rapidly with a high proportion of young people. Whether growing or not, the global population now faces new challenges to its sustainability from climate change and ageing.

Demographers supervise the collection of statistics on population – from censuses, surveys and administrative registers. They build mathematical models to project the numbers to be expected in the future and document the geographical distribution of the present population, often further sub-divided by employment, educational and socio-economic status, ethnic group or religion. Demographers are also interested in living arrangements between the cradle and the grave, in households, families and settlements. These foster the conditions of childbearing, survival and well-being. They are, too, key pillars of the social structure on which culture and policies are built. Demography takes account of the sex as well as the age of the people composing a population, partly because of the different roles women and men play in producing the next generation and the often-different rates at which males and females die. Biologically, there are about 105 boys born for every 100 girls, although the cultural environment has led to more boy children in some Asian contexts, while biological and lifestyle differences have led to a predominance of older women across the globe, especially marked in western countries. Any imbalance in numbers of young men and women has implications for the marriage or partnership ‘market’.

 “Demography is, at its core, about measuring and modelling the change or stability of global and local populations.”

While the low economic and educational status of women may have helped sustain high fertility in poor countries, it is now observed that rich countries which empower women to combine economic roles and parenthood, such as in Scandinavia, are among those avoiding the lowest, ‘sub-replacement’ fertility as observed in Southern Europe and Eastern Asia.

The understanding of the causes and consequences of population change is an interdisciplinary endeavour, embracing a wide range of expertise. Demography is, at its core, about measuring and modelling the change or stability of global and local populations. The ‘demographics’ of the pollster are just one manifestation of the uses and importance of this activity. Although it does not feature in many undergraduate curricula, demography is a vital component of the social science armoury, and will be in continuing demand from international organisations, national and local governments, not to mention academic and market research.


Heather Joshi is Professor Emerita at the Centre for Longitudinal Studies, UCL Institute for Education. She is an economic demographer, and former director of the Millennium Cohort study. She is Executive Editor of Longitudinal and Life Course Studies. She was elected a Fellow of the British Academy in 2000 and is chair of the Sociology, Demography and Social Statistics section.

Further reading:

What is demography? Expert essays from the International Union for the Scientific Study of Population

Blog • Sociology • Heather Joshi FBA