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Editor's note: This story was originally posted in the March 2004 issue, and has been reposted to highlight the long history of Nobelists publishing in Scientific American.
Most American and French citizens—indeed, those of democracies the world over—spend little time contemplating their voting systems. That preoccupation is usually left to political and electoral analysts. But in the past few years, a large segment of both these countries’ populations have found themselves utterly perplexed. People in France wondered how a politician well outside the political mainstream made it to the final two-candidate runoff in the presidential election of 2002. In the U.S., many voters asked why the most popular candidate lost the election of 2000.
We will leave discussions of hanging chads, butterfly ballots, the electoral college and the U.S. Supreme Court to political commentators. But based on research by ourselves and colleagues, we can address a more fundamental issue: What kinds of systems, be they for electing national leaders or student council presidents, go furthest toward truly representing the wishes of the voters? We argue that one particular system would be best in this sense—and it would be simple and practical to implement in the U.S., France and myriad other countries.
The Importance of Being Ranked
IN MOST NATIONAL presidential electoral systems, a voter chooses only his or her favorite candidate rather than ranking them all. If just two candidates compete, this limitation makes no difference. But with three or more candidates, it can matter a great deal. The French presidential election of 2002 provides a case in point. In the first round, voters could vote for one of nine candidates, the most prominent being the incumbent Jacques Chirac of the Gaullist party, the Socialist leader Lionel Jospin and the National Front candidate Jean-Marie Le Pen. The rules dictated that if no candidate obtained an outright majority, the two candidates with the largest numbers of votes would face each other in a runoff. Chirac finished first (with 19.9 percent of the vote). The real surprise, however, lay in second place: the far-right-winger Le Pen took it (with 16.9 percent), while Jospin—who, with Chirac, had been heavily favored to reach the runoff—finished third (with 16.2 percent). In the second round, Chirac handily defeated Le Pen.
Despite Jospin’s third-place finish, most available evidence suggests that in a one-to-one contest against Le Pen, he would have easily won. It is even plausible that he could have defeated Chirac had he made it to the second round. Yet by having voters submit only their top choice, the French electoral system cannot take account of such important information. Furthermore, it permits extremist candidates such as Le Pen—candidates who have no real chance of winning—to have an appreciable effect on the outcome.
The 2000 U.S. presidential election exposed similar shortcomings. To make this point most clearly, we will pretend that the election procedure was simpler than it actually was. We will consider just the four main candidates, and we will assume that there is no difference between the popular vote and the electoral college vote. (There have been many complaints about the electoral college, but even if it were replaced by popular vote, serious problems would remain.) We will also assume that there are only four kinds of voters: those who prefer Ralph Nader to Al Gore, Gore to George W. Bush, and Bush to Pat Buchanan (the “Nader” voters); those with the ranking Gore, Bush, Nader, Buchanan (the “Gore” voters); those with the ranking Bush, Buchanan, Gore, Nader (the “Bush” voters); and those with the ranking Buchanan, Bush, Gore, Nader (the “Buchanan” voters). To be concrete, suppose that 2 percent of the electorate are Nader voters, 49 percent Gore voters, 48 percent Bush voters, and 1 percent Buchanan voters. If voters each choose one candidate, Gore will receive 49 percent and Bush 48 percent of the total (the actual percentages were 48.4 percent and 47.9 percent, respectively). Given that no candidate receives a majority (that is, more than 50 percent), how is the winner to be determined? Gore receives a plurality (the most votes short of 50 percent), so perhaps he should win.