Power Indexes in Voting Systems and Multiple-Valued Logic

In case of majority voting situation such as assembly or a general meeting of shareholders, the analysis of the actual power about the number of the seats or the shares is important because it may strongly affect the future strategy of the organization. We take up the Banzhaf index as a tool to analyze the power of votes and consider it from the standpoint of logic functions. A ternary power index which is an extension of the Banzhaf index is defined because actual majority voting systems are usually based on ternary logic. It is applied to the diet of our nation showing the difference to the binary result.