When a poor index becomes a good proxy: on the predictive value of individual fertility preferences at the cohort macro-level

Establishing a link between fertility prospects and aggregate fertility is a widespread concern, with most of the literature dating from the 1970s-80s. Long time-series on fertility preferences are however scarce, and first attempts are made here of looking at the correlation between cohort aggregate preferences and actual cohort completed fertility on a series of definitions of fertility prospects (intended number of children, ideal and societal ideal family size). We use a set of French surveys: past surveys on demographic situation (Ined), more recent surveys on family (Ined/Insee/Inserm), and a yearly time-series of ideal family size (CREDOC). Mean “societal” ideals are found the closest to completed cohort fertility in terms of level. We use the only consistent time-series on ideals (CREDOC) in order to model the link more precisely. In terms of trends, it appears that completed fertility and ideal family size are quite linked together, while ideals do not predict accurately period total fertility rate.