Electing a Single Winner: Approval Voting in Practice

It may come as a surprise to some that there is a science of elections, whose prov­ enance can be traced back to the Marquis de Condorcet in eighteenth-century France, Charles Dodgson (Lewis Carroll) in nineteenth-century England, and Kenneth Arrow in twentieth-century America. Since Arrow published his semi­ nal book, Social Choice and Individual Values, more than fifty years ago (Ar­ row, 1951, 1963)—for which in large part he received the Nobel Memorial Prize in Economics in 1972—there have been thousands of articles and hundreds of books published on everything from the mathematical properties of voting sys­ tems to empirical tests of the propensity of different systems to elect centrist candidates.1 The 2000 U.S. presidential election highlighted, among other things, the frailties of voting machines and the seeming arbitrariness of such venerable U.S. institutions as the Electoral College and the Supreme Court. Political com­ mentary has focused on these aspects but given very little attention to alterna­ tive voting systems, about which the science of elections has much to say. Several alternative systems for electing a single winner have been shown to be far superior to plurality voting (PV)—the most common voting system used in the United States as well as in many other places—in terms of a number of cri­ teria. PV, which allows citizens to vote for only one candidate, suffers from a dismaying flaw. In any race with more than two candidates, PV may elect the candidate least acceptable to the majority of voters. This frequently happens in a three-way contest, when the majority splits its votes between two centrist candi­ dates, enabling a candidate on the left or right to defeat both centrists. PV also