The use of population censuses to correct the distribution of births by order of the civil registration system. application to Spanish Data in the 1975-2005 Period

Daniel Devolder, Universitat Autònoma de Barcelona
Marta Merino, Universitat Autònoma de Barcelona
Rocio Treviño-Maruri, Universitat Autònoma de Barcelona

The availability of accurate birth statistics by order and duration is a requisite for the application of new fertility measures proposed in the last fifty years, which provide better estimates of the mean number of children than the Total Fertility Rate. These new measures also allow the calculation of fertility level by order, which is useful in the light of the recent evolution in most European countries characterized by an increase in childlessness levels. For example the proportion of women childless reaches 18% for younger generations in Spain, and more than 20% in several Central European Countries and other Mediterranean countries like Italy. Working extensively with this kind of data for different countries, we were able to observe that the classification of birth by order is not always accurate, due to the relative complexity of the form or methodological problems at the National Statistical Institutes. We show in this work how to use Population Censuses in order to reconstruct the birth order and to estimate national yearly series of births classified by order and age of the mother, applying a method similar to the so-called 'own-children method'. Using the three most recent Spanish population censuses, we are able to show that there are indeed severe problems in these statistical data, and that around 8% of the births classified at the first order are indeed of higher order. This leads us to obtain new estimates of the childlessness levels in Spain, which are significantly higher than those calculated with the official national statistics.