Before the official censuses which begin in 1801 there is no body of records (apart from bills of mortality) compiled primarily to obtain demographic or sociological information. Moreover the historian, unlike the social scientist, cannot create his own raw material, but must use what time and chance have allowed to survive. Nevertheless there is a great variety of sources available, and only the chief ones are dealt with here. Up to 1538 the sources available for the study of population and social structure in England are largely feudal or fiscal in nature; after that, until 1801, they are mainly ecclesiastical. Since such records were compiled for other purposes than the study of demography and social structure, the investigator is faced with a double problem of how reliable the records are even for what they purport to be or to do, and to what extent and in what way they can be utilized to give answers to the questions which interest modern historians.

The first problem requires awareness that administration in the past was often weak, corrupt, and inefficient. Taxes, for example, were evaded, laxly enforced, or became stereotyped. The second problem involves taking into account such considerations as the fact that most tax returns did not cover total population (sometimes omitting those under a certain age, those below a certain income level, those who were not heads of households, and so on). This involves the historian in estimating the proportion of children to adults and of paupers to the rest of the population, the average size of families, and, for this purpose, in employing multipliers.