Strategyproof Sharing of Submodular Access Costs: Budget Balance versus Efficiency

A given set of users share the submodular cost of access to a network (or, more generally, the submodular cost of any idiosyncratic binary good). We compare strategyproof mechanisms that serve the efficient set of users (but do not necessarily balance the budget) with those that exactly cover costs (but are not necessarily efficient). Under the requirements of individual rationality (guarante eing voluntary participation) and consumer sovereignty (an agent will obtain access if his willingness to pay is high enough), we find: