Difference-in-Differences When Treatment Status Is Observed in Only One Period

This paper extends the difference-in-differences method to the setting of repeated cross-sections when treatment status is observed in either the pre- or the post-treatment period, but not in both time periods. The issue in such a setting is that the outcomes that are observed in the period when the treatment status is missing cannot be classified into outcomes for the treated and outcomes for the control. As such, the standard …