Beyond the Facts: Limited Empirical Diversity and Causal Inference in Qualitative Comparative Analysis

Qualitative Comparative Analysis (QCA) is a relatively young method of causal inference that continues to diffuse across the social sciences. However, recent methodological research has found the conservative (QCA-CS) and the intermediate solution type (QCA-IS) of QCA to fail fundamental tests of correctness. Even under conditions otherwise ideal for causal discovery, both solution types frequently committed causal fallacies by presenting inferences that were in direct disagreement with the underlying data-generating structure to be discovered by QCA. None of these problems affected the parsimonious solution type (QCA-PS). These findings conflict with conventional wisdom in the QCA literature, which has it that QCA-CS uses empirical information only and that QCA-IS is preferable to both QCA-CS and QCA-PS. The present article resolves these contradictions. It shows that QCA-CS and QCA-IS systematically supplement empirical data with matching artificial data. These artificial data, however, regularly induce causal fallacies of severe magnitude. Researchers who employ QCA-CS or QCA-IS in empirical analyses thus always risk moving further away from the truth rather than closer to it.