Going beyond the single case: Comparative Process Tracing as a tool to enable generalizations about causal processes

In this article, we develop Comparative Process Tracing (PT) as a strategy for validating empirically the scope of cases to which process-level generalizations can be made. While PT methods have discussed internal validity, there has been less attention given to the external validity of processual claims. Comparative PT involves two phases. The intensive phase involves comparing results from two or more PT case studies, both in terms of whether each part of the process was similar and whether the conditions were similar. If a different process is found, then the analysis should focus on identifying the difference between the cases that accounts for different processes. If the causal process operating in the two initial cases is similar, we move to the extensive phase, where the researcher conducts PT ‘light’ studies of ever more diverse cases to explore empirically the bounds of valid processual generalizations.