Cumulative voting

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Cumulative voting (sometimes called the single divisible vote) is a election system where a voter casts multiple votes but can lump votes on a specific candidate or can split their votes across multiple candidates. The candidates elected are those receiving the largest number of votes cast in the election, up to the number of representatives to be elected.

Cumulative voting can simplify strategic voting, by allowing larger groups of voters to elect multiple representatives by splitting their vote between multiple candidates. This removes the complexity associated with randomized or coordinated strategies.

It may be thought of as a variant of block voting. Under both cumulative voting and block voting, a voter casts multiple votes but in the case of cumulative voting, can lump them all on one candidate (the equivalent of engaging in plumping). When voters do this, the result is similar to SNTV. When supporters of a minority candidate do this, they may be of sufficient strength to elect that minority representative, not a likely occurrence under either first past the post voting or block voting. Thus, cumulative voting generally produces similar results to SNTV (especially if voters are informed and rational, in which case they will tend to engage in plumping. Plumping though reduces cumulative voting's effectiveness at releasing voters from need for strategic voting by engaging in vote splitting.).

Cumulative voting can also be thought of as a form of cardinal voting: a variant on score voting where the total scores for each candidate must add up to a fixed value (e.g. 100%). If instead the sum of squares must add up to a fixed value, the method becomes quadratic voting.^[1][2]

Cumulative voting is semi-proportional, allowing for more representative government than winner-take-all elections using block plurality voting or block instant-runoff voting. Cumulative voting is commonly-used in corporate governance, where it is mandated by 7 U.S. states.^[3]

The method can also be used in participatory budgeting.^[4]