Correction for underestimation of fertility by standard of living measured from the Permanent Demographic Sample (EDP)

Following the publication of a first study of fertility by standard of living (Insee Première n°1826 "The most modest and well-off women have the most children", November 2020), this working document explains the methodology used and proposes methodological improvements. It also updates the results of the study with these improvements.

The first part presents a method intended to correct the underestimation of fertility as observed in the previous study, carried out from the EDP – the Permanent Demographic Sample, a large-scale socio-demographic panel established in France. The underestimation of fertility stems from an incomplete matching of births from the Civil Registry with the women present in the socio-fiscal data of the EDP, a matching necessary in order to study fertility according to standard of living. It is the reinjection of initially unmatched births which, after adjustment, makes it possible to find a level of fertility comparable to the reference level of the demographic report. This method makes it possible, from the EDP, to have a more appropriate basis for carrying out studies on fertility according to different characteristics. More generally, the work carried out shows that an incomplete match is not necessarily an obstacle, and that non-identifying variables can be used to fill in the missing information.

The second part explains the indicator chosen to measure fertility according to standard of living. This is the ICFRA – total fertility rate taking into account the birth order and age, constructed from the fertility rates by age observed in a given year for each birth order. Given certain constraints linked to the EDP, special optimization of the field of the study is necessary in order to have a sufficiently large sample of women while being able to use the variable relating to the number of children already born.

The third and fourth parts revise the results, without calling into question the conclusions of INSEE Première on fertility according to standard of living. In particular, the results at the bottom of the living standards scale and for foreign-born women are significantly revised upwards. This document also completes them, with two more recent years or more detailed cross-tabulations of variables.