The Survival-Probability Indices of Period Total Fertility Rate

Kazuo Yamaguchi, University of Chicago
Motomi Beppu, Reitaku University

This article shows that the tempo effect on period total fertility rate (PTFR) measured by the conventional index includes two elements, which we call genuine tempo bias and spurious tempo bias. Genuine tempo bias exists between complete cohort fertility rate (CFR) and any measure of PTFR when the tempo of fertility changes over time, while spurious tempo bias exists in the conventional index as bias that greatly inflates genuine tempo bias. We identify the cause of spurious tempo bias, formally assess the relative weight of spurious tempo bias in the tempo effect, and propose two survival probability indices of PTFR that eliminate spurious tempo bias without making any strong assumption. As a side product, we also introduce a new index which improves the adjusted TFR index introduced by Bongaarts and Feeney. An application of the new and old indices to Japanese fertility data for the past 20 years is presented.