Uncertainty, Complexity, and Gamson’s Law: Comparing Coalition Formation in Western Europe

According to Gamson’s Law, the allocation of cabinet portfolios in parliamentary democracies is proportional to the legislative seat shares of the governing parties. However, portfolio allocation departs systematically from perfect proportionality. This paper proposes a theory of portfolio allocation that seeks to explain the variance in proportionality across different bargaining situations. It argues that the degree to which the coalition formation process is characterised by uncertainty and complexity influences portfolio allocation. In uncertain and complex bargaining situations, parties that otherwise would be in an advantageous bargaining position will have a difficult time exploiting their bargaining advantage. As a result, portfolio allocation in such circumstances will be closer to proportionality. These patterns are observed in data on coalition formation in 14 West European parliamentary systems in the period 1945–1999.