The slow accumulation of completed reconstitutions by the Cambridge Group was a haphazard process. Those who volunteered to undertake a reconstitution made a choice from a list of parishes which had appeared prima facie to possess suitable registers. Alternatively, a local historian might write describing a register in which he or she was interested and suggest that a reconstitution was feasible. Such offers were normally accepted provided that further tests demonstrated that the register was indeed capable of sustaining a successful reconstitution, at least for a substantial period of time. There could therefore be no prior expectation that the set of reconstitutions would prove to reflect the behaviour of the nation as a whole. Such a coincidence was most unlikely. Nor did this seem unfortunate since the individual reconstitutions were intended to reflect extremes of local experience which would establish the extent of the variability of demographic characteristics, as they reflected local economic, geographical, and cultural peculiarities. Remote, upland pastoral economies; market towns engaged in handicraft industry and providing services; centres of early industrial growth; villages dependent chiefly on arable agriculture; such communities might be expected to differ from one another considerably.

Initial investigation, however, suggested that the improbable was happening as the total of reconstitutions reached and passed the two dozen mark. Just as with the 404 parishes which contributed data to the aggregative study, so with the reconstitution parishes, an attempt was made to collect certain standard items of information to enable the distinctive features of each parish to be specified.