Over the last thirty years parish registers have been used with great effect to throw light on the population history of England. To decide whether a parish register was suitable to be used for such purposes systems were developed to assess the quality of that register, and in particular to assess whether a satisfactory percentage of the baptisms, marriages and burials that took place in that parish are likely to have been entered in the parish register. However, until recently relatively little consideration has been given to the quality of the individual entries in a parish register, and still less as to why entries of above average quality appear in a given register. This paper is concerned with the extended parish registers that are to be found in the late eighteenth and early nineteenth century, in particular the so-called Dade registers that are to be found in the dioceses of York and Chester, which contain substantially more information than most parish registers of the period. It will, it is hoped, lead to a clearer understanding of these registers and make local historians and demographers more aware of their potential.