In This Article Expand or collapse the "in this article" section 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: 26 March 2020
  • LAST MODIFIED: 22 April 2020
  • 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 enables only 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

To understand what process tracing is as a distinct case study method, it is important to have a good working knowledge of the underlying realist philosophical foundations of case-based methods. A wonderful and comprehensive introduction to different philosophical foundations of different social science methods can be found in Jackson 2016. Good introductions to realist philosophy can be found in Maxwell 2012 and Sayer 2000. It is also important to understand the core methodological debates about what case studies actually are. After the publication of Designing Social Inquiry (King, et al. 1994), considerable debate has arisen 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 is articulated in 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 ontological and/or epistemological foundations different from “variance-based” approaches. The “variance-based” approach to case studies—including process tracing—is described in King, et al. 1994 and in 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.

  • Beach, Derek, and Rasmus Brun Pedersen. Causal Case Study Methods: Foundations and Guidelines for Comparing, Matching and Tracing. Ann Arbor: University of Michigan Press, 2019.

    The book explores the foundational differences between case-based and variance-based approaches and develops a set of guidelines for using case-based comparative methods and process tracing.

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

    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: MIT Press, 2005.

    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.

    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.

    A very useful introduction to the core elements of case-based methods taken as a whole. Less helpful regarding how to use process tracing in practice.

  • Jackson, Patrick Thaddeus. The Conduct of Inquiry in International Relations: Philosophy of Science and Its Implications for the Study of World Politics. 2d ed. London: Routledge, 2016.

    DOI: 10.4324/9781315731360

    Influential book that explores the foundational philosophical assumptions underlying social science methodologies, including neopositivism, (critical) realism, pragmaticism and analyticism, and reflexive approaches.

  • Johnson, R. Burke, Federica Russo, and Judith Schoonenboom. “Causation in Mixed Methods Research: The Meeting of Philosophy, Science, and Practice.” Journal of Mixed Methods Research 13.2 (2019): 143–162.

    Useful overview article that discusses different understandings of causation, including a mechanistic account that is distinguished from counterfactual and regularity accounts.

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

    DOI: 10.1515/9781400821211

    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.

  • Maxwell, Joseph A. A Realist Approach for Qualitative Research. Thousand Oaks, CA: SAGE, 2012.

    Great introduction to realist philosophy that develops an interpretivist epistemological stance while at the same time arguing for process understandings of causation as well as causal complexity.

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

    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.

    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.

  • Sayer, Andrew. Realism and Social Science. London: SAGE, 2000.

    DOI: 10.4135/9781446218730

    Concise introduction to critical realism that develops the distinctions between the real-actual-empirical, and that discusses the nature of causal mechanisms.

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