In this article, a new methodology that employs parity-progression ratios to estimate the effect of female sterilization on fertility is described, and results using data from Ecuador are compared to those obtained using a previously existing approach that classifies women by marital duration. The methods differ in how they disaggregate marital fertility and in the assumption they make about what the subsequent fertility of sterilized women would have been if they had not been sterilized. The analysis of the Ecuadoran data shows that the estimate of births averted by sterilization has diminished over time, even as sterilization prevalence has been increasing. This situation is attributed to a decline in the fertility of nonsterilized women resulting from increased use of reversible methods of contraception.
PIP: Two methods are used to show the impact on fertility of sterilization: births averted in a single five-year period before the survey and the parity progression ratio approach for 1979-84 and 1984-89 used to estimate births averted by birth order and duration since first union. The births averted analysis revealed that fertility among nonsterilized women declined from 5.93 in 1979-84 to 5.01 in 1984-89. The births averted approach showed almost no change in total births averted and a shift in the distribution of births averted by marital duration. Births averted were greater during 1984-89 among marital durations under 15 years and during 1979-84 at marital durations of 15-24 years. The actual percentage of ever married women who were sterilized increased over the decade, but the hypothetical proportions being sterilized in a given duration remained almost unchanged. This approach underestimated births averted, because it did not account for future declines in fertility among nonsterilized women. The parity progression ratio (PPR) approach indicated a nonsterilized fertility decline of 1.28 births per woman and a marital fertility decline of 1.04 births. Between the two periods, sterilization contributed to a reduction of 0.24 births. The preferred PPR approach accounted for the effects of sterilization on individual PPRs and proportions of ever-married women. This method offered consideration of increased sterilization prevalence, but declining births averted by sterilization. A comparison of both methods shows that the parity progression approach yielded higher estimates of the average number of births averted by sterilization and higher total nonsterilized marital fertility rates (total marital fertility rates in the absence of sterilization). Marital fertility rates remained similar. Data are obtained from the 1989 Ecuador Demographic and Health Survey and the World Fertility Surveys of 1979 and 1989.