1. INTRODUCTION

The term ‘family’ is used widely in everyday speech, almost invariably unquestioningly, as though an unambiguous unique definition is selfevident. Most people would understand a family to include members who are related by blood or marriage, and most would probably add those connected through cohabitation. Yet this definition, based as it is upon biological parenthood, kinship and sexual relationship, is not completely clear-cut: for example, should adoptive and non-resident stepchildren and students away at college be included, and where should the line be drawn with distant relatives? It is evident, too, that an individual can have links to more than one family, and that families are formed through social, as well as biological, parenthood.

For demographic purposes, the issue is partly solved by contemplating a variety of alternative definitions ranging from the ‘nuclear’ family to the ‘extended’ family. Two additional criteria can usefully be considered: sharing a common residence (even if on an occasional or part-time basis); and emotional ties of affection, care or support. Of course, these factors may, or may not, coincide: for example, an elderly relative living nearby may receive help and support, while a member of the ‘extended’ family may live in the same household, but yet lead an entirely separate and independent existence from those of the ‘nuclear’ family.

More generally, sociologists and social theorists have devoted considerable energy to identifying the different types of families, and postulating how their evolution is related to developments in society and individuals’ changing needs and roles. Their approach has been from a number of different perspectives: biological, functional, social, psychological, and political/ideological, as well as from an anti-family stance. Understandably, most of the available statistical information on families refers to coresidential members, primarily because censuses and surveys are addressed to those resident in particular households, which in turn are easy to locate because each occupies a fixed physical space. Indeed, the concepts of family and household were scarcely distinguishable in official statistics up to 1961, when a definitive typology was first introduced into the census, becoming the standard basis for subsequent classifications.