Combining process tracing and synthetic control method: Bridging two ways for making causal inference in case studies

This paper discusses potential methods of triangulation between two leading methods for case-study research: synthetic control (SC) method and process tracing (PT) method. Both are designed to examine certain events that occur in given cases but view these events from different causal perspectives. Seeing an event as a cause, SC estimates its impact on one or more outcomes. Conversely, seeing an event as an outcome, PT discloses the causes which generated it. Hence, one can start from the causal explanation reached via one of the two methods and then proceed to examine that explanation through the other method. Once the causes of an event are traced via a PT analysis, that account can be validated by estimating the effects of those causes via SC. Equally, once the impact of a certain event is estimated through SC, causal mechanisms traceable via PT can be exploited to refine that impact evaluation.