We study efficiency and fairness properties of the equal cost sharing with maximal
participation (ECSMP) mechanism in the provision of a binary and excludable public good.
According to the maximal welfare loss criterion, the ECSMP is optimal within the class of
strategyproof, individually rational and no-deficit mechanisms only when there are two
agents. In general the ECSMP mechanism is not optimal: we provide a class of mechanisms
obtained by symmetric perturbations of ECSMP with strictly lower maximal welfare loss. We …

We study effi ciency and fairness properties of the equal cost shar% ing with maximal
participation (ECSMP) mechanism in the provision of a binary and excludable public good.
According to the maximal welfare loss criterion, the ECSMP is optimal within the class of
strategyproof, individ% ually rational and no% budget% deficit mechanisms only when there
are two agents. In general the ECSMP mechanism is not optimal: we provide a class of
mechanisms obtained by symmetric perturbations of ECSMP with 1We thank María Angeles …