Duggan–Schwartz theorem

The Duggan–Schwartz theorem is a result in the field of social choice theory, specifically concerning the aggregation of preferences in social welfare functions. It addresses the impossibility of certain desirable properties in the context of collective decision-making. In its essence, the theorem states that under certain conditions, it is impossible to create a social welfare function that satisfies all of the following criteria: 1. **Unrestricted Domain:** Any individual preference order can be taken as input.