How can social planners prevent disappointment in an election?

Mechanism design is concerned with settings where a policy maker (or social planner) faces the problem of aggregating the announced preferences of multiple agents into a collective (or social), system-wide decision. One of the most important ways for aggregation preference used in a multi agent system is using election. In an election, the aim is to select the candidate who reects the common will of the whole society. Despite the importance of this subject, in the real world situations, sometimes under special circumstances, the result of the election is completely an antithesis of the purpose of those who execute it or the election leads to the dissatisfaction of a large amount of people. For analyzing these situations, a notion is discussed in the present paper called social disappointment and then new protocols are proposed to prevent social disappointment. A version of the impossibility theorem is stated and proved regarding social disappointment in elections. In the end, the numerical results obtained by simulating the voting protocols of plurality and Hare system are given, to show that Hare system is a little more seccessful than plurality to prevent social disappointment.