Synthetic Controls with Staggered Adoption

Eli Ben-Michael, Avi Feller and Jesse Rothstein

No 28886, NBER Working Papers from National Bureau of Economic Research, Inc

Abstract: Staggered adoption of policies by different units at different times creates promising opportunities for observational causal inference. Estimation remains challenging, however, and common regression methods can give misleading results. A promising alternative is the synthetic control method (SCM), which finds a weighted average of control units that closely balances the treated unit’s pre-treatment outcomes. In this paper, we generalize SCM, originally designed to study a single treated unit, to the staggered adoption setting. We first bound the error for the average effect and show that it depends on both the imbalance for each treated unit separately and the imbalance for the average of the treated units. We then propose "partially pooled" SCM weights to minimize a weighted combination of these measures; approaches that focus only on balancing one of the two components can lead to bias. We extend this approach to incorporate unit-level intercept shifts and auxiliary covariates. We assess the performance of the proposed method via extensive simulations and apply our results to the question of whether teacher collective bargaining leads to higher school spending, finding minimal impacts. We implement the proposed method in the augsynth R package.

JEL-codes: C21 C23 I21 J5 (search for similar items in EconPapers)
Date: 2021-06
New Economics Papers: this item is included in nep-ecm and nep-ore
Note: ED LS PE TWP
References: Add references at CitEc
Citations: View citations in EconPapers (17)

Published as Eli Ben-Michael & Avi Feller & Jesse Rothstein, 2022. "Synthetic Controls with Staggered Adoption," Journal of the Royal Statistical Society Series B: Statistical Methodology, vol 84(2), pages 351-381.

Downloads: (external link)
http://www.nber.org/papers/w28886.pdf (application/pdf)

Related works:
Journal Article: Synthetic controls with staggered adoption (2022)
Working Paper: Synthetic Controls with Staggered Adoption (2021)
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:nbr:nberwo:28886

Ordering information: This working paper can be ordered from
http://www.nber.org/papers/w28886

Access Statistics for this paper

More papers in NBER Working Papers from National Bureau of Economic Research, Inc National Bureau of Economic Research, 1050 Massachusetts Avenue Cambridge, MA 02138, U.S.A.. Contact information at EDIRC.
Bibliographic data for series maintained by ().