We consider the use of difference in differences (DD) to evaluate the effect of an activity assistance program on the health of severely disabled Koreans. There are, however, 2 problems in the data: the number of response categories for self-assessed health changed over the waves of the repeated cross-section survey and the “parallel untreated response path” assumption for DD is suspect. We show how to overcome these problems by renormalizing parameters and applying “generalized difference in differences (GDD).” We find a significantly positive effect of the program with DD, but not with GDD. Our solutions should prove useful in applications in which one or other of these problems arise.
Bibliographical notePublisher Copyright:
Copyright © 2017 John Wiley & Sons, Ltd.
- difference in differences
- generalized difference in differences
- ordinal response
- self-assessed health
ASJC Scopus subject areas
- Health Policy