Scoring rules, condorcet efficiency and social homogeneity

In a three-candidate election, a scoring rule lambda, lambda is an element of[0,1], assigns 1,lambda and 0 points (respectively) to each first, second and third place in the individual preference rankings. The Condorcet effic iency of a scoring rule is defined as the conditional probability that this rule selects the winner in accordance with Condorcet criteria (three Condo rcet criteria are considered in the paper). We are interested in the follow ing question: What rule lambda has the greatest Condorcet efficiency? After recalling the known answer to this question, we investigate the impact of social homogeneity on the optimal value of lambda. One of the most salient results we obtain is that the optimality of the Borda rule (lambda=1/2) hol ds only if the voters act in an independent way.