Before revision:  The synthetic control method (SCM) is a recent addition to the evaluation toolkit but is designed to study a single treated unitand does not easily accommodate staggered adoption .
After revision:  Estimation remains challenging, however, and common regression methods can give misleading results. A promising alternative is the synthetic control method (SCM) is a recent addition to the evaluation toolkit but is designed to study a single treated unitand does not easily accommodate staggered adoption .