Statistics have very seldom been collected for purely historical analysis. They have normally been collected to assist in such functions as administration, planning, and levying taxes. Historians by the very nature of their subject are forced to use other people's statistics. They cannot redesign the surveys and questionnaires that were used in the past, they cannot measure things that were not measured or affect the timing and location of those surveys, censuses, investigations and registrations that were carried out. They have to make the best use of what statistical data and accounts are available to them. Before they begin using these data, however, they should attempt to discover how the data were collected and calculated, and by whom these operations were carried out. They should attempt to see whether there are any reasons for doubting the reliability of these data. Where doubts do arise as to their reliability, they should attempt to make an assessment of the possible scale of the inaccuracy. It is extremely dangerous to accept figures on trust without understanding their origin and history.

These homilies apply to the study of the economic and social development of any country at any time. They are even more important in the case of Soviet history. It is true that Western historians working on the economic and social history of the USSR have the advantage of dealing with a country that had a well-developed central statistical agency and was gathering and publishing data on all sorts of social phenomena.