Reaching Closure
Two issues are important in reaching closure: when to stop adding cases, and when to stop iterating between theory and data. In the first, ideally, researchers should stop adding cases when theoretical saturation is reached. Theoretical saturation is the point at which incremental learning is minimal because the researchers are observing phenomena seen before. In practice, theoretical saturation often combines with pragmatic considerations such as time and money to dictate when case collection ends. In fact, it is not uncommon for researchers to plan the number of cases in advance. In the second closure issue, when to stop iterating between theory and data, again, saturation is the key idea. That is, the iteration process stops when the incremental improvement to theory is minimal. The final product of building theory from case studies may be concepts, a conceptual framework, or propositions or possibly midrange theory. On the downside, the final product may be disappointing. The research may simply replicate prior theory, or there may be no clear patterns within the data.
The process of building theory from case study research is a strikingly iterative one. One strength of theory building from cases is its likelihood of generating novel theory. A second strength is that the emergent theory is likely to be testable with constructs that can be readily measured and hypotheses that can be proven false. A third strength is that the resultant theory is likely to be empirically valid. The likelihood of valid theory is high because the theory-building process is so intimately tied with evidence that it is very likely that the resultant theory will be consistent with empirical observation.