Implications of the Effective Number of Parties for Cabinet Formation

This note helps to explain how cabinet-level concentration of power is constrained by party level concentration of seats. Arend Lijphart's Patterns of Democracy (1999) measures concentration of executive power by the frequency of minimal winning and one-party cabinets (MW/OP), and party concentration by the effective number (N) of legislative parties. In his factor analysis, these highly correlated indices are the central features that distinguish consensual from majoritarian systems. The present study establishes a quantitative logical relationship leading from N to the major component of MW/OP, so as to explain the reasons behind Lijphart's empirical observation. The note analyses separately the frequency of various types of cabinet coalitions that Lijphart's book has lumped together. It also offers a new way to visualize the effective number of legislative parties, as twice the minimal number of parties needed to form a minimal winning coalition. © 2002, Sage Publications. All rights reserved