Case Studies and Theory Development in the Social Sciences - Alexander L. George [112]
Process-tracing may be a unique tool for discovering whether the phenomenon being investigated is characterized by equifinality (or “multiple convergence” as it is referred to by some scholars). Process-tracing offers the possibility of identifying different causal paths that lead to a similar outcome in different cases. These cases, in turn, can serve as building blocks for empirical, inductive construction of a typological theory.434 Process-tracing encourages the investigator to be sensitive to the possibility of equifinality. Case studies employing process-tracing are particularly useful as a supplement in large-N statistical analyses, which are likely to overlook the possibility of equifinality and settle for a statement of a probabilistic finding regarding only one causal path at work.
Process-tracing is particularly useful for obtaining an explanation for deviant cases, those that have outcomes not predicted or explained adequately by existing theories. Deviant cases are frequently encountered in large-N studies and usually noted as such without an effort to explain why they are deviant. Process-tracing of deviant cases offers an opportunity to differentiate and enrich the general theory. Witness, for example, the exemplary study of the International Typographical Union (I.T.U.) by Seymour Martin Lipset, Martin Trow, and James S. Coleman. They noted that the record of the I.T.U. contradicted the “iron law of oligarchy” advanced by Robert Michels in his classic study, Political Parties, which argued that inherent in any large-scale social organization were motivations and means that led leaders of its bureaucratic structure to place protection and exercise of their position ahead of commitment to democratic internal procedures. Contradicting the generalization, the I.T.U. governed itself through an elaborate and largely effective democratic system. The I.T.U., as Lipset describes it in a subsequent “biography” of their study, was an example of what he later learned that Paul Lazarsfeld called a deviant case. The authors’ study of the I.T.U. investigated whether there were new or specific factors present in this deviant case that explained its departure from the iron law of oligarchy. A historical-structural study of the I.T.U. employing survey research data and making some use of process-tracing uncovered causal mechanisms and social and psychological processes that provided an explanation for the special deviant character of the union.435
The identification and analysis of deviant cases and of cases characterized by equifinality are useful for developing contingent generalizations that identify the conditions under which alternative outcomes occur. The importance of developing conditional generalizations of limited scope, a form of middle-range theory, is emphasized at various points in the present study.436
In developing a theory about a particular phenomenon such as deterrence via analytic induction, as in the Alexander George and Richard Smoke study (summarized in the Appendix, “Studies That Illustrate Research Design”), process-tracing provided an explanation for each of the small number of cases examined. At the outset, each case was regarded as a possible deviant case. When explanations for the outcome of individual cases vary, the results can be cumulated and contribute to the development of a rich, differentiated theory about that phenomenon.
Assessing Predictions
If a theory is sufficiently developed that it generates or implies predictions about causal processes that lead to outcomes, then process-tracing can assess the predictions of the theory. In this use, process-tracing evidence tests whether the observed processes among variables in a case match those predicted or implied by the theory. To be sure, as noted earlier in this chapter, many available theories have not been