The three variants of process tracing methods and their uses and limitations
We argue that a lot of the murkiness about what Process Tracing (PT) actually is and how it should be used in practice can be cleared up by identifying three variants of PT within political science: theory-testing PT, theory-building PT, and explaining outcomes PT. The three can be differentiated along several dimensions, including whether they are theory- or case-centric, the types of inferences being made, how they understand causal mechanisms, and whether and how they can be nested in mixed-methods designs. The differentiation of PT into three variants has important implications for how and when we use PT case studies. First, there are differences in what we are actually tracing in the three variants, resulting in different methodological prescriptions for each variant. Second, the types of inferences being made are also different; the variants therefore have different analytical uses. And finally, the three variants differ as regards whether they can be nested into mixed-methods research designs. In theory-testing PT, a more general causal mechanism is being traced in the case study; a mechanism that is expected to function across a bounded-set of contexts. Here the findings of a single case study can potentially be exported and compared with other cases, enabling theory-testing studies to be nested within mixed-methods designs. In contrast, explaining outcome PT cannot be nested in mixed-methods designs.
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American Political Science Association Annual Meeting 2011