This variable contains the administrative birthdate for the last biological child. The universe for this variable is all women between the ages of 15 and 65 at the time of the fertility history topical module. This variable was created by first looking for biological children on the SIPP household roster and choosing the birthdate of the youngest child (if no children were found, the value was set to missing). The total number of biological children reported on the roster (could possibly be zero) was then compared to the woman's report in her fertility history about the number of children born to her. If the number born to her was larger, last_admin_birthdate was set to missing and imputed using the woman's report of the last year she gave birth as a predictor variable. This process allowed us to create a fertility history that was consistent with the children reported on the roster and their administrative birthdates but still handle cases where older children or all children lived outside the household.