Variables The data consists of fertility rates, given for each year (1882-1954) of births per 1000 ever-married women by single years of age, 15 to 49. The data was derived by matching vital statistics on birth with data on population exposed to risk, which came in part from population censuses and in part from intercensal estimation. Please note: this study does not include information on named individuals and would therefore not be useful for personal family history research.