How many persons to a household? Many demographers have asked themselves this since Guichardin, Vauban, and Quételet: hence a considerable literature devoted to the subject. Historians are perpetually brought back to this issue because north of the Alps the practice of numbering households is more widespread than that of nominal censuses. Thus fiscal returns have been preserved which contain the numbers of hearths liable to tax (fouages, haertsteden or tockages) for whole provinces, whereas lists called by clergymen status animarum or censuses of souls, which provide accounts of every individual, household by household, in a single parish were scarcely ever made up by the parish priests of Western Europe. Who can resist the temptation to calculate the ratio of inhabitants to households in a document of this kind where the evidence is certain, in order to use it as a multiplier elsewhere?

Alas, this expedient which seems to be so simple, is full of pitfalls. There are uncertainties in the boundaries which surrounded communities in earlier times; there are the random fluctuations, which are always extreme in societies subject to famines and epidemics; there are exemptions from taxation, omissions of children, or of those not subject to the jurisdiction of the incumbent of a parish. Father Roger Mols has sifted the published results for scores of European towns, and fifteen years after it was delivered his authoritative critical judgement retains its relevance.