The role of reproductive ageing in the widening gap between desired and achieved fertility: theoretical considerations and empirical results

Krzysztof Tymicki, Warsaw School of Economics

The gap between desired and achieved fertility might be caused by many demographic and social factors such as: values and preferences surrounding family formation process, housing or availability of partners on the marriage market. Paper focuses on one of the biological factors affecting the gap, namely reproductive ageing. Taking into account postponement of reproduction in developed countries, we may expect increase in incidence subfecundity (at all parities), leading to achieved fertility below planned. Frequently demographic studies ignore this and assume perfect recuperation. Due to reproductive ageing, this assumption could be violated and achieved fertility might diverge from planned. Paper proposes a framework for analyzing impact of biological factors on the gap between desired and achieved fertility along with convenient way of measuring reproductive ageing with use of waiting-time-to-pregnancy to assess magnitude of decrease in fecundity. Theoretical considerations are illustrated with empirical results from large scale survey studies.