Process tracing can be defined as:

“The analysis of evidence on processes, sequences, and conjunctures of events within a case for the purposes of either developing or testing hypotheses about causal mechanisms that might causally explain the case.” Bennet and Checkel 2015, p. 7

It is a methodology that combines pre-existing generalisations with specific observations from within a single case to make causal inferences about that case (Mahoney 2012). It involves the examination of ‘diagnostic’ pieces of evidence within a case to support or overturn alternative explanatory hypotheses; the identification of sequences and causal mechanisms is central (Bennett 2010).

What is involved?

Ricks and Liu (2018) set out the series of steps involved in process tracing:

1. Identify hypotheses: The evaluator draws on broader generalisations and evidence from within the case to generate a series of (preferably competing) testable hypotheses about how an intervention may connect to an outcome. A Theory of Change exercise that has preceded the process tracing may provide a useful starting point for the generation of hypotheses.

2. Establish a timeline: Understanding the chronology of events is an important first step in analysing causal processes.
Construct a causal graph: A causal graph visually depicts the causal process through which X causes Y and follows the timeline. It identifies the independent variable(s) of interest and provides structure to the process of enquiry by showing all the points at which the relevant actor (an individual, an organisation or a group) made a choice that could have affected the result.

3. Identify alternative choices or events: At each relevant moment in the causal graph, a different choice could have been made. These alternatives should be identified.

4. Identify counterfactual outcomes: Counterfactuals are vital to process tracing.

5. Find evidence for the primary hypothesis: There is no single type of data collection method specified for process tracing. Data collection should be designed to match the evidence specified in the hypotheses being tested. Data collection involves in-depth case study analysis and, thus, is likely to be predominantly qualitative, including historical reports, interviews and observations, but quantitative data may also be used.

6. Find evidence for rival hypotheses: The final step is to repeat step 6 for each alternative explanation.
Download a Process Tracing case study here
Download a longer briefing on Process Tracing here

Useful resources

For a short overview of process tracing see:

Bennett, A. (2010) ‘Process Tracing and Causal Inference’ in Brady, H. and Collier, D. (Eds.) Rethinking Social Inquiry, Rowman and Littlefield.

For a practical guide to undertaking process tracing:

Ricks, J. I. and Liu, A. H., 2018. ‘Process-tracing research designs: a practical guide’. PS: Political Science & Politics, 51(4), 842–846.

Ricks and Lui have placed a number of worked examples online to accompany their 2018 article on process tracing. These follow the same steps set out in their article and can be accessed here.