Democratic societies change. Historically, processes such as immigration, changes in the territory of a state, and changes in the franchise, among others, have added new groups of individuals to and subtracted existing groups of individuals from a democratic state's citizenry. Over time, countries have become more or less socially heterogeneous as a result, and at any one given time, some countries have been more socially heterogeneous than others. A natural question to ask is how these changes in social heterogeneity have shaped the democratic party system. This is the overarching research question with which I have been concerned in this book.

In this chapter, I offer final thoughts about the effect of social heterogeneity upon party system fragmentation, the dimension of the party system and hence the specific research question that has been my primary focus. Based on the arguments I have developed and the empirical analyses I have undertaken in the preceding chapters, what can we say about how social heterogeneity shapes this dimension of the party system? Even more specifically, what can we say about when new latent social groups will successfully manage to form their own sectarian political parties? This is the key mechanism by which, I have argued, social heterogeneity shapes party system fragmentation and the second and arguably more fundamental research question with which I have been concerned. The answer in a nutshell is that we can say a fair amount: several systemic factors explicitly not limited to the electoral system combine with features of the new social groups themselves to determine the likelihood that these groups will succeed at forming sectarian parties, and hence to determine what the effect of increases in social heterogeneity upon party system fragmentation will be. However, there are still areas in need of attention from future researchers.