La question de l'identification des échelles d'équivalence : une estimation du coût de l'enfant sur des données de panel.

The identification question raised by Lewbel in the estimation of equivalence scales is empirically discussed using Polish panel data for two sets of four consecutive years (1987-90 and 1997-2000). The value of the equivalence scale estimates varies considerably when dynamics of family formation changes is taken into account. The estimations also show that some expenditures depend on the expectation of the arrival or departure of family members. Estimates for the second, post transition panel, yield for cross-section a somewhat different level of the equivalence scale, compared to the first panel covering the transition period, contrary to the similarity of time-series estimates for the two data-sets. This may prove that the cost of children and adults estimated on cross-section are largely determined by economic environment changes.