This concluding chapter is divided into two parts. In the first section, I summarize the central arguments and findings. In the second section, I identify some of the questions that still remain to be answered and offer some preliminary thoughts on the implications of various levels of aggregation for policymaking processes and outcomes.

SUMMARY OF KEY FINDINGS

In this book, I have focused on two dimensions of a country's party system – the number of parties and the degree of the nationalization. I have attempted to broaden the debate beyond the behavior of voters, candidates, and parties within electoral districts to include a focus the coordination of such actors across districts. I argued that aggregation is a key determinant of both the size of the party system and the degree of nationalization. Thus it is important to understand what factors shape the degree of aggregation.

The causal logic of my argument was grounded in the incentives of party entrepreneurs and candidates for political office. Aggregation is a function of the incentives these actors face to ally across districts under a common party banner. These incentives, in turn, are shaped by (1) the potential payoff for aggregation and (2) the probability of capturing that payoff. The incentives for coordinating across districts increase as the rewards for such coordination rise and the degree of uncertainty about capturing that reward falls.