Although an interest in illegitimacy as a societal phenomenon is often limited by the scarcity of data, we may utilize recognized procedures of standardization in estimating illegitimacy ratios and rates where none are reported.
When we know only the age-specific marital status of women in the childbearing years (15 to 44) we may utilize age-specific legitimate and illegitimate fertility rates of the high and low illegitimacy countries, Jamaica and Japan, to estimate the range within which a national ratio would fall. In all there are sixty-eight major countries of the world for which we have that minimum data on age and marital status of females.
Some of those countries also report the number and percentage of illegitimate births but offer no information on age-specific rates. In those cases we may compare the ratios produced by the four model sets of rates (run against actual age and marital status for the sixty-eight nations) with the ratio actually reported by individual countries. Where the ratio produced by a model matches the reported ratio, with similar crude birth rates, we may assume similar age-specific legitimate and illegitimate fertility rates. Even where there is no perfect match we still learn something of the general pattern of rates.
Finally, the output of the standardization procedure also allows a comparison of the relative importance of marital status versus differential illegitimate fertility rates in determining the percentage of births out of wedlock.
While we must recognize the problems inherent in international comparisons of illegitimacy, the subject is of such significance that we cannot and we need not wait for more, or more perfect, data to be available. Rather, an increased interest in maximizing whatever comparative data we do find, may, in itself, aid in the improvement of methods and reliability of collection and publication of relevant information.