The Robustness of Cohort Effects in Age Period Tables

This paper clarifies and provides additional tests presented in the age-period-cohort analysis of nonmarital birth rates in Gray, O'Brien, Stockard, and Stone(forthcoming). Where Martin (forthcoming) has suggested specific alternative specifications or interpretations of our findings, we have re-estimated and performed explicit tests of the alternatives. In the end we demonstrate the robustness of our results and have strengthened the case for our interpretations. The points Martin (forthcoming) raises and our responses clarify the nature of cohort effects and our interpretation of them. We thank Martin for his close attention to our paper.