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Abstract:
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Elections rely on people, hardware, and software: all are fallible and subject to manipulation. Uncertainty about election outcomes has been weaponized politically in the last 18 months. How can we conduct elections in a way that provides affirmative evidence that the reported winners really won? Such "evidence-based elections" require trustworthy voter-marked paper ballots. Two kinds of audits are required to provide affirmative evidence that outcomes are correct: compliance audits to check whether the paper trail is complete and trustworthy, and risk-limiting audits (RLAs). RLAs test the hypothesis that an accurate manual tabulation of the votes would find that one or more reported winners did not win. For a broad variety of social choice functions including all "scoring rules," the hypothesis that one or more outcomes is wrong can be reduced to the hypothesis that the mean of one or more lists of nonnegative numbers is not greater than 1/2. Martingale methods are especially practical. There have been roughly 60 pilot or binding RLAs in jurisdictions of all sizes, including about a dozen RLAs of statewide contests. Open-source software to support RLAs is available.
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