The right way to read Ranked-choice ballots: not Instant Runoff, but Ranked Pairs-B
Summary: The four linked papers A through D analyze how best to take ranked-choice ballots and choose a single winner. The analysis includes the different incentives each method offers to candidates, causes, and voters, seeking to win, particularly to the tactics of bracketing and strategic nomination; presents examples and proofs of how the different methods perform when voters opinions are described as ranging along more than one political axis; and how the different systems rate against all the various abstract criteria used to assess the worth of election systems. In sum, any tournament method is decisively better than Instant Runoff (also known as the Alternative vote, or the Hare method); and the best of the tournament methods is Ranked Pairs; it is argued that any tournament method better than Ranked Pairs is unlikely to exist, which given its ease of implementation, makes it the best choice if ranked-choice ballots are to be used. Ranked Pairs works whether voters preferences on their ballots are strict, or whether voters are permitted to rank candidates in equal groups. If Ranked Pairs is considered too different from Instant Runoff to adopt, two other runoff methods, the Direct Hybrid and the Benham method, may be used instead.
Description: Paper B covers six key points. (1) Instant Runoff is vulnerable to bracketing, a whereby a candidate who would defeat any one rival by an overwhelming margin loses when challenged by several. (2) Under Instant Runoff, running many candidate of diverse views does not increase how well the opinions of the election winner match those of the electorate; under Condorcet methods, it does. (3) Mathematical theorems, the median lemma and its generalizations, guarantee that the candidate closest to the median opinion will win under Condorcet methods, even when many issues matter to voters. (4) There is sound reason to suppose that electing this closest-to-median candidate is, in the broadest sense, highly desirable. (5) Condorcet methods promote desirable behavior even in candidates who value nothing but winning. (6) The theory justifying points (1) to (5) is not novel but decades old.
