In This Article Process Tracing Methods

  • Introduction
  • Debates about Case Studies and Case-based Methods
  • Case Selection and Combining Process Tracing with Other Methods

International Relations Process Tracing Methods
Derek Beach
  • LAST REVIEWED: 23 December 2019
  • LAST MODIFIED: 22 February 2018
  • DOI: 10.1093/obo/9780199743292-0227


Process tracing is an in-depth within-case study method used in the social sciences for tracing causal mechanisms and how they play out within an actual case. Process tracing can be used to build and test theories of processes that link causes and outcomes in a bounded population of causally similar cases, in combination with comparative methods, or, when used in a more pragmatic fashion, to gain a greater understanding of the causal dynamics that produced the outcome of a particular historical case. The strength of process tracing is that detailed knowledge is gained through the collection of within-case, mechanistic evidence about how causal processes work in real-world cases. Process tracing only enables within-case inferences to be made, making comparative methods necessary to enable inferences to causally similar cases. Comparisons make generalization possible because we can then claim that as a set of other cases are causally similar to the studied one, we should expect similar mechanisms to also be operative in these cases. Process tracing as a method can be broken down into three core components: theorization about causal mechanisms linking causes and outcomes, the development and analysis of the observable empirical manifestations of the operation of parts of theorized mechanisms, and the complementary use of comparative methods to enable generalizations of findings from single case studies to other causally similar cases.

Debates about Case Studies and Case-based Methods

In order to understand what process tracing is as a distinct case study method, it is vital to have a good working knowledge of the methodological debates about what case studies actually are. After the publication of Designing Social Inquiry (King, et al. 1994), there has been considerable debate about whether small-n methods, including case studies and small-n comparisons, constitute a distinct research approach, or whether they can be subsumed under an overarching logic of studying variance. The “case-based” approach has been articulated by Brady and Collier 2011, George and Bennett 2005, Goertz and Mahoney 2012, Ragin 1987, and Ragin 2000, among others. This approach argues that small-n comparisons and within-case study methods like process tracing build on different ontological and/or epistemological foundations than “variance-based” approaches. The “variance-based” approach to case studies—including process tracing—is described by King, et al. 1994, and by Gerring 2017. Here single cases are disaggregated into multiple “cases” in order to assess the difference that variance in values of a cause (or intervening variables) have for values on the outcome across units of the case.

  • Brady, Henry E., and David Collier, eds. Rethinking Social Inquiry: Diverse Tools, Shared Standards. 2d ed. Lanham, MD: Rowman Littlefield, 2011.

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    Influential edited volume that explores different aspects of case-based research, including differences with variance-based approaches, and discussions of what types of evidence within-case analyses can use.

  • George, Alexander L., and Andrew Bennett. Case Studies and Theory Development in the Social Sciences. Cambridge, MA, and London: MIT, 2005.

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    Influential book that developed core ideas about process tracing as a distinct research method, along with structured, focused comparisons and congruence case studies.

  • Gerring, John. Case Study Research. 2d ed. Cambridge, UK: Cambridge University Press, 2017.

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    Introduction to case study methods from a variance-based perspective.

  • Goertz, Gary, and James Mahoney. A Tale of Two Cultures: Qualitative and Quantitative Research in the Social Sciences. Princeton, NJ: Princeton University Press, 2012.

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    A useful introduction to the core elements of case-based methods. Less helpful regarding how to use process tracing.

  • King, Gary, Robert O. Keohane, and Sidney Verba. Designing Social Inquiry: Scientific Inference in Qualitative Research. Princeton, NJ: Princeton University Press, 1994.

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    Classic but controversial book that argues that cases should be disaggregated into multiple “cases” in order to investigate the difference that variance in the values of independent and intervening variables makes for the outcome.

  • Ragin, Charles C. The Comparative Method: Moving beyond Qualitative and Quantitative Strategies. Berkeley: University of California Press, 1987.

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    Classic book that develops some of the foundations for case-based methods.

  • Ragin, Charles C. Fuzzy-Set Social Science. Chicago: University of Chicago Press, 2000.

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    Book that introduces more advanced comparative techniques (qualitative comparative analysis, QCA) within case-based methods. QCA is a useful tool in combination with within-case studies using process tracing.

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