On the structure of the political party system in Indian states, 1957–2018

We develop and test an equilibrium model of party structure to account for the large and ever-changing number of political parties that contest Indian state elections. The analysis finds that the number of parties increases with the voting density of state constituencies, the heterogeneity of the state’s electorate, state per capita income and literacy levels, falls with average age while responding to a set of constitutional and legislative rules designed to affect party and electoral performance. The model is also applied to entry and exit, allowing the empirics to highlight those factors that affect party turnover rather than aggregate party numbers. The model explains better the number of parties than ENP, the effective (vote share weighted) number of parties, implying that the variability in the fringe of smaller parties has not substantially affected the vote shares received by the larger more established parties. Affirmative action, primarily in the form of increases in the proportion of seats reserved for members of special castes is associated with a reduction in both party numbers and ENP consistent with speeding the integration of scheduled castes into broader based political parties.