The basic data used in an earlier paper, on very nearly all the national life tables ever published, are applied here to several additional questions. The first two sections examine some past and prospective effects of mortality changes on potential size of the labour force and on net reproductivity. Sex differentials are reviewed next, with attention to their direction, trends, variations by age and regional comparisons. The last section takes up three propositions : (1) that the ratio of persons in the main labour-force age group to total numbers is practically constant in stationary populations; (2) that infant mortality is a “sensitive indicator” of mortality conditions in general; and (3) that mortality changes tend to be “comparatively small” at older ages. These propositions are tested for empirical validity and lead to some inferences of general demographic interest.