COWPEA (Candidates Optimally Weighted in Proportional Election using Approval voting)

Abstract: This paper describes COWPEA (Candidates Optimally Weighted in Proportional Election using Approval voting), a method of proportional representation that uses approval voting, also known as random priority, though underdeveloped in the literature. COWPEA optimally elects an unlimited number of candidates with potentially different weights to a body, rather than giving a fixed number equal weight. A non-deterministic Approval-Based Committee (ABC) version that elects a fixed a number of candidates with equal weight is known as COWPEA Lottery. This is the only method known to pass the criteria of monotonicity, strong candidate Pareto efficiency, Independence of Irrelevant Ballots, and Independence of Unanimously Approved Candidates. It is also possible to convert COWPEA and COWPEA Lottery to score or graded voting methods. COWPEA and COWPEA Lottery are also compared against Optimal PAV and Optimal PAV Lottery.