Advances in the P/F ratio method for the analysis of birth histories

Abstract One of the most frequently used indirect techniques for deriving estimates of recent fertility from simple questions in censuses and surveys is the 'P/F ratio' method. Availability of detailed birth-history data, as in the World Fertility Survey, and applications of the P/F procedure as a diagnostic tool in the evaluation of the quality of data have led to simplifications and extensions of the original method. This analysis illustrates that when complete maternity histories are available, the P/F procedure can be simplified and made more powerful by (1) calculation of P/F values from cohort-period fertility rates and (2) use of two further indexing variables, namely duration since first marriage and duration since first birth, in addition to age. More generally, the paper indicates that a set of P/F values is only one of a battery of measures which aid in the analysis of trends and errors in data from maternity histories. Illustrative examples are given from various analyses of world Fertility Survey data. Howard Goldberg has been independently pursuing an investigation of the P/F procedure by marriage duration at the Office of Population Research (Princeton University), and we have profited from recent discussions with him. We would also like to acknowledge useful comments and criticisms on earlier drafts from James Trussell and Kenneth Hill.     

Estimating fertility trends from retrospective birth histories: Sensitivity to imputation of missing dates

Abstract In the birth history section of the Core Questionnaire adopted by the countries participating in the World Fertility Survey a question on the date of birth of each child born to the respondent is asked. When the woman cannot provide a date, as is often the case in many developing countries, she is asked how many 'years ago' the birth occurred. If the default is used, the month and year of the birth is imputed by a computer program: However, there can be two plausible interpretations of the 'years ago' response: as completed years, the demographer's usual definition of age, or as rounded years. In this paper, data from the WFS Survey in Bangladesh are used to determine the sensitivity of recent fertility estimates to the interpretation of 'years ago'. It is found that if the woman meant rounded years, but completed years were assumed for imputation, the resulting evidence of a recent decline could be either exaggerated or false. The results have implications for other surveys in which the 'years ago' response is not an explicit option.