To evaluate theories about the impact of electoral law on party systems, it is useful to have an indicator of exactly how many parties are competitive in a given election. Several formulae convert the vote shares won by multiple parties into single number-of-parties indices. While these formulae are typically applied to national vote shares, it is often more revealing to examine constituency-level data. For some purposes, the calculated value for the number-of-parties-in-the-nation is a poor substitute for a fuller description of how many parties or candidates exist, constituency by constituency.
- Competition indices
- Electoral districts
- Party systems
ASJC Scopus subject areas
- Political Science and International Relations