Key points

• Demography is the scientific study of human populations.

• It is important to understand the structure of a population in order to plan health and public health interventions; population structures can be represented as age pyramids.

• Population growth or decline depends upon fertility, mortality and migration.

• The concepts of demographic, epidemiological and health transitions help explain dramatic shifts in population structure and patterns of disease that have taken place in most countries.

• The measurement of demographic statistics is difficult and modelling is used to provide comparable data across the world.

Introduction

Demography is the scientific study of human populations. It involves analysis of three observable phenomena: changes in population size, the composition of the population and the distribution of populations in space. Demographers study five processes: fertility, mortality, marriage, migration and social mobility. These processes determine populations’ size, composition and distribution. Basic understanding of demography is essential for public health practitioners because the health of communities and individuals depends on the dynamic relationship between the numbers of people, the space which they occupy and the skills they have acquired. The main sources of demographic information vary between countries and they are well developed in the western hemisphere.