ABSTRACT
Demography is concerned with description of the size, composition and structure of populations (usually human) and how these change with time. Statisticians are interested in patterns of births, deaths, marriages and migration (event counts) and the distribution of attributes such as age, sex, social class, and family size. Demographic techniques are also of some use in ecological surveillance where there is interest in the breeding stability of a colony of birds or animals or where concern exists over culling programmes or the depletion of fish stocks. The relative importance of these factors in different countries (and even in the UK) remains the subject of much debate among economic and social historians. A pictorial representation of the age–sex structure of a population at a particular time is provided by an age–sex profile or population pyramid. The diagram can portray actual numbers in the age–sex classes so that differences in total population size are apparent.
