The course and causes of aggregate population change were intimately interwoven into the fabric of society and economy of later-medieval Essex. And yet it is precisely these demographic patterns that have proved most elusive to historians of the period. Sources affording reliable estimates of the scale and chronology of local population change and the factors that influenced it, let alone estimates that bear comparison with the historical demography of other times and places, are exceedingly scarce and opaque in England before the mid-sixteenth century. But the central and northern district of Essex has left records pertaining to demographic measures that, cumulatively, are unique for England as a whole. It is by no means the case that these sources can unequivocally answer all the questions one might wish to ask about the demographic system of the later middle ages. Within the limits imposed by their very nature and that of derivations made from them, however, their answers are remarkably consistent.

In many Essex communities during the period the system of frankpledge required that resident adolescent and adult males be enrolled into groups called tithings. From sixteen communities in the district, the numbers of males in tithing can be reconstructed on a year-to-year basis, in some cases from the late thirteenth to the late sixteenth century, constituting an index of aggregate population change. With minor variations there is substantial agreement among the series.