Social Choice Functions

Abstract

Social choices, by which we mean group or collective decisions, are made in twoways. In political voting, collective decision is typically used to make “political” decisions, and in the market mechanism, collective decision is typically used to make economic decisions. In this chapter, we concentrate exclusively on the former. Collective action (or social [group] choices) should be based on the preferences of individuals (or agents) in society. Therefore, an important aspect of social choice theory is a description and analysis of the way preferences of individual members of a group are aggregated into a decision of the group as a whole (see Arrow 1950; and Taylor 2005). We are interested in aggregating preferences of the agents into a social decision, which essentially means that we consider social choice functions that, for each possible individual preference profile, picks an alternative for society from the set of alternatives. This approach is different from social welfare function (discussed in Chapters 2–6) that for each possible individual preference profile picks an ordering for society (not just an alternative like the social choice function).