On the Buyability of Voting Bodies

IMF Working Papers, July 1, 2007

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Study of vote buying by competing interest groups in a variety of electoral and contractual settings.
Increasing the size of a voting body reduces its buyability in the absence of competition.
Larger voting bodies may be more buyable than smaller voting bodies when interest groups compete.
Imposing the secret ballot—modeled as forcing interest groups to contract on outcomes rather than votes—is an effective way to fight vote buying in the presence of competition, but much less so in its absence.
The option to contract on both votes and outcomes is worthless, as it does not affect buyability as compared to contracting only on votes, regardless of competition.
When interest groups can contract on votes and vote shares, voting bodies are uniquely at risk of being bought.

Effect of voting body size:
- Increasing size reduces buyability when there is no competition among interest groups.
- Increasing size can increase buyability when interest groups compete.
Secret ballot impact:
- Secret ballot (contracting on outcomes rather than votes) effectively deters vote buying under competition.
- Secret ballot has much less deterrent effect in the absence of competition.
Contracts examined:
- Contracts contingent on votes alone.
- Contracts contingent on outcomes alone.
- Contracts contingent on both votes and outcomes: no additional effect compared to contracting only on votes.
- Contracts contingent on votes and vote shares: create unique vulnerability to buyability.

Electoral design and procurement of voting bodies should consider competitive dynamics among interest groups; larger bodies are not universally less buyable.
Expanding the use of secret ballots can be an effective anti–vote-buying measure principally when interest groups compete.
Regulatory focus on the form of contracting matters: allowing contracts on vote shares introduces distinct risks not present with simpler vote-only or outcome-only contracts.