A family may be defined as a group of persons “related, to a specified degree, through blood, adoption, or marriage”. The same source states: “The degree of relationship used in determining the limits of the family is dependent upon the uses to which the data are to be put and so cannot be precisely set for world-wide use”.

To the extent that ties of blood, marriage, or adoption are indicative of a community of interest of members, whatever their location, the family, in this broad sense, is an important unit in economic analysis – since it presumably makes joint decisions on the production and disposition of income, either in a continuous and comprehensive fashion, or intermittently and over a limited range. The possibility of such joint action makes the family unit useful in the study of income inequalities, of the supply of labor force, and of the flow of savings and capital formation.

The difficulty is that there are no comparative data on the family in the broad definition of the term. The available statistics relate to households, defined by location and by community of arrangements for providing essentials of living. The data usually cover all households, not limited to family households, although the latter are such a preponderant proportion that the characteristics of the totals can be identified as those of family households. The statistical analysis undertaken here is confined to data on households.