STICERD Econometrics Seminar Series
Synthetic Difference in Differences
Stefan Wager (Stanford University)
Thursday 21 November 2019 14:00 - 15:30
Many of our seminars and public events this year will continue as in person or as hybrid (online and in person) events. Please check our website listings and Twitter feed @STICERD_LSE for updates.
Unless otherwise specified, in-person seminars are open to the public. Please ensure you have informed the event contact as early as possible.
Those unable to join the seminars in-person are welcome to participate via zoom if the event is hybrid.
About this event
We present a new perspective on the Synthetic Control (SC) method as a weighted least squares regression estimator with time fixed effects and unit weights. This perspective suggests a generalization with two way (both unit and time) fixed effects, and both unit and time weights, which can be interpreted as a unit and time weighted version of the standard Difference In Differences (DID) estimator. We find that this new Synthetic Difference In Differences (SDID) estimator has attractive properties compared to the SC and DID estimators. Formally we show that our approach has double robustness properties: the SDID estimator is consistent under a wide variety of weighting schemes given a well-specified fixed effects model, and SDID is consistent with appropriately penalized SC weights when the basic fixed effects model is misspecified and instead the true data generating process involves a more general low-rank structure (e.g., a latent factor model). We also present results that justify standard inference based on weighted DID regression. Further generalizations include unit and time weighted factor models.
Related
STICERD Econometrics seminars are held on Thursdays in term time at 14.00-15.30, in SAL 3.05, unless specified otherwise.
Seminar organisers: Dr Yike Wang, Professor Tai Otsu, and Dr Vassilis Hajivassiliou.
For further information please contact Sadia Ali: s.ali43@lse.ac.uk.
Please use this link to subscribe or unsubscribe to STICERD Econometrics mailing list (emetrics).