Before revision: In political science, the effective number of parties is a diversity index introduced by Laakso and Taagepera (1979) which provides for an adjusted number of political parties in a country's party system, weighted by their relative size.
After revision: Rein,In political science, the effective number of parties is a diversity index introduced by Laakso and Taagepera (1979) which provides for an adjusted number of political parties in a country's party system, weighted by their relative size.