THE CONDORCET EFFICIENCY OF APPROVAL VOTING AND THE PROBABILITY OF ELECTING THE CONDORCET LOSER

The Condorcet winner in an election is an alternative that would defea t each of the other alternatives in a series of pairwise elections. Th e Condorcet efficiency of a voting rule is the conditional probability that the voting rule will elect the Condorcet winner, given that a Co ndorcet winner exists. The paper assumes the impartial culture conditi on for large electorates and shows that approval voting has greater Co ndorcet efficiency than plurality rule, and that it has smaller Condor cet efficiency than the voting rule in which voters must vote for half of the available alternatives. The likelihood that election rules sel ect the Condorcet loser is also considered. (C) 1998 Elsevier Science S.A.