Most Similar Systems Design
The most similar systems design (MSSD) is a small-N comparative strategy that selects cases as alike as possible on many background characteristics but differing on the outcome of interest. By matching cases so that most potential confounders are held roughly constant, the design isolates the few factors that vary alongside the outcome as the candidate causes. Rooted in John Stuart Mill's method of difference and named by Przeworski and Teune, it is a cornerstone of comparative politics for drawing causal inferences from a handful of countries or cases.
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Sources
- Przeworski, A., & Teune, H. (1970). The Logic of Comparative Social Inquiry. New York: Wiley-Interscience. ISBN: 9780471701422
- Seawright, J., & Gerring, J. (2008). Case Selection Techniques in Case Study Research: A Menu of Qualitative and Quantitative Options. Political Research Quarterly, 61(2), 294–308. DOI: 10.1177/1065912907313077 ↗
- Gerring, J. (2007). Case Study Research: Principles and Practices. Cambridge: Cambridge University Press. ISBN: 9780521676564
How to cite this page
ScholarGate. (2026, June 22). Most Similar Systems Design (Comparative Method of Difference). ScholarGate. https://scholargate.app/en/political-science/most-similar-systems-design
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Most Different Systems DesignPolitical Science↔ compare
- Process TracingPsychometrics↔ compare
- Qualitative Comparative AnalysisPolitical Science↔ compare