Data submitted on the questionnaires are supplemented, to the extent possible, by data taken from official national statistical publications and by correspondence with the national statistical services. In the interest of comparability, data presented as rates, ratios, and percentages are calculated in the Statistical Offices of the United Nations, except for life table functions and a few exceptions in the rate tables, which have been appropriately noted in the Demographic Yearbook . The current edition, Demographic Yearbook 1995, is the forty-seventh issue of this comprehensive compilation of demographic and related statistics. Copies of the data files for each issue of the Demographic Yearbook , plus several data series of special subject areas, are available for purchase. Demographic Yearbook 1980 and subsequent issues are available.
Special extracts are also available.