Adrian Vatter, "Legislative Party Fragmentation in Swiss Cantons: A Function of Cleavage Structures or Electoral Institutions?," Party Politics, 9 (July 2003),445-461.

First Paragraph:
One of the classic questions in political science is: what determines the numbers of parties in differing social and political systems? In contrast to most studies up to now, my approach is not by way of an international comparison, but instead by analysis of the subnational level of Swiss states (cantons). A comparative analysis of the two dozen cantonal political systems provides an opportunity to assess the ever more important question for established democracies concerning the determinant factors of growing political fragmentation. It also plays an important role for the new democracies of Eastern Europe, which find themselves in the midst of a transformation process. The limits and possibilities of institutional engineering become especially meaningful for building the party structure (Lijphart, 1994)

Figures and Tables:
Table 1: Correlations between the number of legislative parties and different predictor variables
Table 2: Results for multiple regression models (OLS method, regression coefficients; N=24). Dependent variable: number of effective parties in parliament (Laakso-Taagepera index)

Last Paragraph:
The main findings of this analysis can be summarized as follows: the more rural agrarian, less densely settled, more religiously uniform and smaller the district magnitudes are in a canton, the smaller the number of legislative parties. On the other hand, the more urban, the more religiously diverse and the lower the effective thresholds are in a canton, the larger the number of parties in cantonal parliaments. [First paragraph in conclusion.]