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Qualitative Comparative Analysis (QCA) is a new analytic technique that uses Boolean algebra to implement principles of comparison used by scholars engaged in the qualitative study of macrosocial phenomena. Typically, qualitatively oriented scholars examine only a few cases at a time, but their analyses are both intensive -- addressing many aspects of cases -- and integrative -- examining how the different parts of a case fit together, both contextually and historically. By formalizing the logic of qualitative analysis, QCA makes it possible to bring the logic and empiricalintensity of qualitative approaches to studies that embrace more than a handful of cases--research situations that normally call for the use of variable-oriented, quantitative methods.

Boolean methods of logical comparison represent each case as a combination of causal and outcome conditions. These combinations can be compared with each other and then logically simplified through a bottom-up process of paired comparison. Computer algorithms developed by electrical engineers in the 1950s provide techniques for simplifying this type of data. The data matrix is reformulated as a "truttable" an reduced in a way that parallels the minimization of switching circuits (see Charles Ragin, The Comparative Method: Moving Beyond Qualitative and Quantitative Strategies). These minimization procedures mimic case-oriented comparative methods but accomplish the most cognitively demanding task -- making multiple comparisons of configurations -- through computer algorithms. The goal of the logical minimization is to represent -- in a logically shorthand manner -- the information in the truth table regarding the different combinations of conditions that produce a specific outcome.

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Working papers by Charles Ragin: $5.00 each

• "Introduction to Qualitative Comparative Analysis" (WP-92-31)

  This paper provides an overview of a new method of data analysis, Qualitative Comparative Analysis (QCA), that uses Boolean algebra to examine causal configurations. QCA was developed as a formalization of the qualitative methods used by comparative researchers in studies of small sets of cases (e.g., involving Ns of two to seven cases). By formalizing these methods, it is possible to extend qualitative methodology to research involving more than a mere handful of cases. Distinctive features of small-N, qualitative methods include: their attention to (1) cases as configurations, (2) causal conjunctures, (3) causal heterogeneity, especially "multiple conjunctural causation" (Ragin 1987), (4) deviating cases, (5) qualitative outcomes, and (6) outcome complexity. This paper shows how algorithms adapted from electrical engineering can be used to aid a daunting cognitive task--multiple comparisons of configurations of characteristics.
  

• "A Qualitative Comparative Analysis of Pension Systems" (WP-92-32)

  Four major objectives structure this paper: (1) to present an application of Qualitative Comparative Analysis (QCA) to audiences interested in the political economy of the welfare state in advanced capitalist societies, (2) to show how to incorporate interval-scale causal and outcome variables in QCA, using principles drawn from cluster analysis, (3) to evaluate Gosta Esping-Andersen's (1990) recent claim that there are three basic types of welfare capitalism, using data on pension systems, and (4) to examine the causes of the diversity of pension systems, using QCA. The major substantive conclusions are that the diversity of pension systems is much greater than that allowed by Esping-Andersen's tripartite scheme and that the main outline of the "political class struggle" explanation of diversity of pension schemes is correct (see also Palme 1990). The paper also offers strong evidence that ethnic and cultural factors, especially ethnic diversity, play an important role in explaining differences among welfare states.