A note on the estimation of intergenerational income correlations by the method of averaging

Averaging methods are routinely used in order to limit biases resulting from the mismeasurement of permanent incomes. The Solon/Zimmerman estimator regresses a single-year measurement of the child's resources on a T-period average of the parents' income while the Behrman/Taubman estimator regresses an S-period average of the child's resources on a T-period average of the parents' income. The latter estimator is shown to be the arithmetic mean of the S slope estimates arising from the Solon/Zimmerman methodology. However, because sampling variation produces yearly changes in the variance of children's incomes, it is shown that the Behrman/Taubman estimator is not efficient in the class of estimators which can be expressed as a weighted sum of the S distinct Solon/Zimmerman estimates. The minimum variance estimator in the above class is thus derived and applied to a US sample.