Empirically supported causal hypotheses are emerging at an increasing rate. Experimental methods have long been useful for establishing cause-effect relationships, and they will continue to be useful, especially for studying variables that operate at the individual and small-group levels. Formal models based on game theory and related approaches continue to be fruitful, but their results will require empirical validation. In the next decade, the field will need to begin to use the developing multicase, multivariate data sets intensively for causal modeling, an approach that was rare in the early years of the field. In moving toward this approach, serious attention will have to be paid to the quality and independence of data on theoretically relevant variables, as well as to the development of time series for individual cases and, ideally, time series on many cases to allow the use of panel analysis methods.
The field will continue to benefit from communication among researchers from different methodological and disciplinary traditions, leading to findings that are robust across research methods. Triangulation of methods is most likely to occur in problem-oriented settings, such as the meetings of the International Association for the Study of Common Property and research projects focused on particular institutional design problems. Affirmative efforts may have to be made to bring together representatives of different research traditions that do not normally communicate. It is also important to encourage communication among research subcommunities focused on different resource types as a way to clarify the breadth of applicability of particular elements of theory. Doing this will be important for applying institutional design theory in new and unfamiliar settings.
As theory develops and is tested against a breadth of data, it becomes possible both to refine concepts, adding more resolution, and to combine concepts. Tietenberg’s investigation (Chapter 6) of tradable permits regimes provides good examples of how careful examination of these regimes led to refinement and differentiation in theory—for instance, to account for the fact that regimes that work well for air pollution do not work so well for fisheries. The discussion of Figure 13-3 earlier in this chapter suggests that cultural heterogeneity, communication, dense social networks, and practices of reciprocity may be part of a cluster of variables that reflect a single underlying construct, such as strength of community or social capital. Although these particular developments in theory may or may not prove fruitful, they do reflect a desirable direction in theory develop-