Introduction How to design and conduct a theory-building case study

9.1.2 Candidate cases

Obviously, candidate cases should be instances from the object of study. The following two principles guide the identification of a smaller set of candidate cases: convenience, and the maximization of the likelihood that an existing relation between the concepts will be discovered. The latter principle requires that one or more sets of can- didate cases be found or constructed which are as similar to each other in all respects apart from the independent and dependent con- cepts from which a proposition should be constructed. A difficulty in achieving this is that in most theory-building research one or both of these concepts are not known. The most efficient way of finding sets of “similar” instances is by identifying small populations in the theoretical domain and selecting cases from such a population.

9.1.3 Case selection

If a small population of similar instances is identified, some instances must be selected from this population in such a way that instances dif- fer as much as possible in terms of the value of the known concept. The number of cases to be selected depends on the type of the con- cepts that are known i.e. concept B in Figure 8.2; concept A in Figure 8.3; concepts A and B in Figure 8.1 and the known variation of the value of these concepts in the list of candidate cases. For instance, if we are interested in discovering as yet unknown success factors for a proj- ect Figure 8.2, it depends on the type of concept B how many cases and what type of cases should be selected. If B is dichotomous pres- ence or absence of success we could begin with just a couple of instances of each possible value e.g. success and lack of success. If B is measured as a rational or interval variable e.g. if success is measured in amounts of money earned, variation in the value of that variable should be maximized. If we are interested in discovering as yet unknown effects of a given condition or intervention A Figure 8.3, it depends on the type of concept A how many cases and what type of cases should be selected. If A is dichotomous, we could begin with just a couple of instances of each possible value e.g. presence or absence of condition A. If A is measured as a rational or interval variable e.g. the size of the workforce or the amount of money spent, variation in the value of that variable should be maximized. If both the concepts A and B are known Figure 8.1, it is recommended to select cases in such a way that the variation in the value of both concepts is maximized. If no concept is known at the beginning of the study as depicted in Figures 8.4 and 8.5, cases cannot be selected on the basis of the varia- tion of these concepts and must, therefore, be selected more or less randomly. Box 12 Michael Porter’s case selection Michael Porter’s theory on The competitive advantage of nations 1990 is based on case study research. Porter and his team wanted to find conditions for a nation’s industries that could explain the success of a nation’s global competitiveness. The theory focused on the strategies of firms rather than the strategies of nations, as “firms, not nations, compete in international markets”. The team selected, from ten important trading nations, the companies that were internationally successful the dependent concept. Then they identified the determinants that could explain the nation’s success the independent concepts. Porter and his team found four determinants four points of a “diamond” of a nation’s success: 1 the nation’s position in factors of production such as skilled labour or infra- structure; 2 demand conditions, the home-market demand for the industry’s product or services; 3 related and supporting industries, the presence or absence in the nation of supplier industries and other related industries that are internationally competitive; and 4 firm strategy, structure, and rivalry, the conditions in the nation governing how companies are created, organized, and managed, as well as the nature of the domestic rivalry. These four determinants are necessary for achieving and sustaining competitive success, or as Porter 1990 : 73 puts it: “Advantages throughout the ‘diamond’ are necessary for achieving and sustaining competitive success in the knowledge-intensive industries that form the backbone of advanced economies”. Porter’s case selection procedures are problematic for two main reasons. One is that, by not including non-successful companies or nations in his study, Porter is not able to distinguish between necessary and sufficient conditions on the one hand, or between necessary and trivial conditions on the other hand. If, for instance, the factors found could exist in any company or sector in an industrialized country, including non-successful ones, this would make the discovered determinants not less “necessary” but it would make them trivial for policy. Apparently, Porter implicitly relies on his readers’ knowledge about conditions in non-successful companies and nations. The second reason is that this form of case selection prohibits finding probabilistic relations. If Porter had found only one single instance without the “necessary” determinants, he would not only have failed to identify the necessary condition but would also not have been able to find another type of relation between determinants and success. Porter’s case selection procedures, thus, were appropriate only for finding candidate necessary conditions and he was lucky to find them.