An estimate of the age structure of London's male population is a crucial first step in estimating the relative size of its citizenry in the middle of the sixteenth century, since the latter is derived by comparing the annual rate of freedom admissions during 1552–3 with an estimate of the total number of men, both free and unfree, who each year entered or were added to the city's adult male population to offset its attrition due to mortality and to account for its net increase in a year. To obtain the latter figures we must first estimate the number of adult males living in London, and data from a model life table were used for that purpose. Though based upon studies of nineteenth- and twentieth-century populations, model life tables provide reasonable approximations of the age structure and other demographic characteristics of early modern populations. There are, however, one hundred tables divided into four models or ‘families’ in the Princeton model life tables, the set used here. Since each table is based upon a specific set of demographic assumptions, the data are useful only if the appropriate table is chosen. The North model was used for the procedure discussed in this appendix, for in his study of the demography of four parishes in early modern London R. Finlay concluded that ‘the North family fits the actual overall mortality experience of these parishes much more closely than the other families’.