Counting the Number of Parties: An Alternative Index

I propose an alternative index to operationalize the variable number and size of parties in a party system. To support it, I present a critical overview of the two most common indices, Laakso and Taagepera's effective number of parties and Kesselman and Wildgen's hyperfractionalization , showing the causes of their weakness. Then I explain the computational logic of my alternative, “number of parties,” and compare it with the other two, using hypothetical cases. After that, I contrast the Laakso-Taagepera index with mine, using data from actual elections between 1945 and 1981. I conclude that my index outperforms the other two as an operationalization of the variable number and size of parties.