Proportional Approval Method using Squared loads, Approval removal and Coin-flip approval transformation (PAMSAC) - a new system of proportional representation using approval voting

Abstract: Several multi-winner systems that use approval voting have been developed but they each suffer from various problems. Six of these methods are discussed in this paper. They are Satisfaction Approval Voting, Minimax Approval Voting, Proportional Approval Voting, Monroe's Fully Proportional Representation, Chamberlin-Courant's Rule, and Ebert's method. They all fail at least one of Proportional Representation (PR), strong PR, monotonicity or positive support. However, the new method described in this paper - Proportional Approval Method using Squared loads, Approval removal and Coin-flip approval transformation (PAMSAC) - passes them all. PAMSAC uses the squared loads of Ebert's method, but removes non-beneficial approvals to restore monotonicity. It also uses the Coin-Flip Approval Transformation (CFAT), where voters are "split" into two for each candidate they approve, and where one half of this split voter approves and the other half does not approve each candidate approved on the ballot. This restores positive support, and also makes the method equivalent to the D'Hondt party-list method for party voting. PAMSAC reduces to simple approval voting in the single-winner case. A score voting version is described that also reduces to simple score voting in the single-winner case.