Choosing a runoff election threshold.

This paper investigates when a runoff election is desirable and when a plurality result is good enough. A runoff election increases the likelihood that the Condorcet winner will be elected but also entails additional costs. The metric for determining whether a runoff election is desirable will be the probability that the winner of the plurality election would win an ensuing runoff. Statistical models of voter behavior are developed that estimate this probability, which are verified with runoff-election data from United States elections. The models allow governments to make more informed choices in creating rules to decide when to hold runoff elections. [ABSTRACT FROM AUTHOR]