Optimally Dictatorial Committees

I study the optimal voting mechanism for a committee that must decide whether to enact or block a policy of unknown benefit. Information can come both from committee members who can acquire it at cost, and a strategic lobbyist who wishes the policy to be enacted. I show that the dictatorship of the most-demanding member is a dominant voting mechanism: any other voting mechanism is (i) less likely to enact a good policy, (ii) more likely to enact a bad policy, and (iii) burdens each member with a greater cost of acquiring information.