This paper provides an expression for the revenue maximizing and open interest maximizing choice of futures contracts by exchanges in incomplete markets under uncertainty, with quadratic Von Neumann-Morgenstern preferences and proportional transactions costs. We characterize the set of Nash equilibria for a number of exchanges simultaneously or sequentially choosing contracts. The optimal monopolistic contract design is shown to be Pareto optimal, while an example shows the failure of Pareto optimality for a set of contracts forming a Nash equilibrium of the multi-exchange design game. Likewise, in a monopolistic multi-period setting, an example shows failure of Pareto optimality, given an incentive for the exchange to induce turnover.