Algorithms for Proportional Representation in Parliament in Divisor and Multiplicative Form

Abstract: We consider three algorithms for allocating parliamentary seats by proportional representation. The usual approach to describing such algorithms is to compute a quota of votes that each party uses to "acquire'' representatives. This kind of description follows a divisor method, since the number of representatives for a party is equal to the number of votes for that party, divided by the quota. We show that a simple multiplicative form with different rounding methods produces algorithms equivalent to the divisor methods. The multiplicative form is intuitive and easier to understand for a wider audience.