The Comparative Method
Comparison is a fundamental tool of analysis. It sharpens our power of description, and plays a central role in concept-formation by bringing into focus suggestive similarities and contrasts among cases. Comparison is routinely used in testing hypotheses, and it can contribute to the inductive discovery of new hypotheses and to theory-building.
The forms of comparison employed in the discipline of political science vary widely and include those contained in statistical analysis, experimental research, and historical studies. At the same time, the label "comparative method" has a standard meaning within the discipline and in the social sciences more broadly: it refers to the methodological issues that arise in the systematic analysis of a small number of cases, or a "small N." 1 This chapter examines alternative perspectives on the comparative method that have emerged over roughly the past two decades. Although the primary focus is on discussions located in the fields of comparative politics and international studies, the application of the comparative method is by no means restricted to those fields.
The decision to analyze only a few cases is strongly influenced by the types of political phenomena under study and how they are conceptualized. Topics for which it is productive to examine relatively few cases include revolutions, particular types of national political regimes (e.g., post-communist regimes), or particular forms of urban political systems. This focus on a small number of cases is adopted because there exist relatively few instances of the phenomenon under consideration that exhibit the attributes of interest to the analyst. Alternatively, some analysts believe that political phenomena in general are best understood through the careful examination of a small number of cases. In the field of comparative and international studies, the practice of focusing on few cases has achieved greater legitimacy in recent years in conjunction with the rise of the school of "comparative historical analysis," in which small numbers of countries are studied over long periods. This close scrutiny of each country limits the number of national cases a scholar can consider. 2
Choosing to study few cases routinely poses the problem of having more rival explanations to assess than cases to observe, or the quandary of "many variables, small N" ( Lijphart 1971, 686). Elementary statistics teaches us that as the number of explanatory factors approaches the number of cases, the capacity to adjudicate among the explanations through statistical comparison rapidly diminishes. This problem has stimulated much discussion of how most productively to analyze a small N.
The late 1960s and early 1970s saw a boom in writing on comparative method (e.g., Merritt and Rokkan 1966; Kalleberg 1966; Verba 1967; Smelser 1968; Lasswell 1968; Przeworski and Teune 1970; Sartori 1970; Merritt 1970; Etzioni and Dubow 1970; Lijphart 1971; Vallier 1971; Zelditch 1971; Armer and Grimshaw 1973). This literature established a set of norms and practices for small-N research, proposed alternative strategies for conducting such analyses, and created a base line of understanding that has played an important role in the ongoing practice of small-N studies. This chapter assesses the issues of comparative method that have been debated in the intervening years and considers their implications for ongoing research. The point of departure is Arend Lijphart ( 1971) article "Comparative Politics and Comparative Method." Among the studies published in that period, Lijphart's piece stands out for its imaginative synthesis of basic issues of comparison and of the relation between comparative method and other branches of methodology. 3 It therefore provides a helpful framework for examining, and building upon, new developments in the field.
A central theme that emerges in the discussion below is that refinements in methods of small-N analysis have substantially broadened the range of techniques available to comparative researchers. The most fruitful approach is eclectic, one in which scholars are willing and able to draw upon these diverse techniques.