Changes in English marriage seasonality reflect, imperfectly, changes in rural economic activity. The great advantage of the method is the extent of the early modern marriage record, a quantitative source continuous over both time and space. The seasonal indices are derived from 542 Anglican marriage registers, roughly 5.4 per cent of English parishes (roughly 5.4 per cent, because of changes in parish boundaries); the proportion of this sample to the surviving total of registers is of course far higher. The sample's foundation is the set that Wrigley and Schofield employed in The Population History of England; I added to it 138 parishes, from original registers and transcripts and gifts from other workers. I employed the raw totals of registered marriages, uncorrected for underregistration. The method of correction employed by Wrigley and Schofield, the application of a national template of monthly seasonality of events, would have served to dampen the regional variations in seasonality that are of interest in this study.

I cannot pretend that the 542 represent a randomly drawn sample of English parishes. To begin with, the Cambridge Group's set is not a random sample; multiple, sometimes mutually inconsistent, guidelines were given to the volunteers who collected the data. Parishes with larger recorded numbers of baptisms, marriages, and burials, for instance, were initially to be preferred to the smaller, to increase the possibility of record-linkage needed to calculate, for example, ages at marriage and age-specific fertility.