Mixed member proportional (MMP) is an electoral system used with some variations in a number of countries, including Germany and New Zealand.

 

The essential idea is that you have two votes: one for your representative, and one for a party. The idea is to combine the benefits of proportional representation (PR: parties with uniform support across the country but less than 50% in any given area still can win representation) and constituency (or electorate) MPs, i.e., a representative accountable to a community.

 

The problem with MMP is that it does not eliminate one of the drawbacks of a pure PR system: parties have a disproportionate say in who gets elected, since a party generally gets to draw up and rank its party list.

Representative Member Proportional Voting

I propose a variant on this system, which I call Representative Member Proportional Voting (RMPV), with several benefits:

• simpler – only one vote required
• community accountability for all MPs
• alternative MPs to call on if the main one is not responsive 

In this model, the first round of counting results in a member of parliament being elected on a first-past-the-post basis. In the second round, all votes countrywide are tallied, to determine the composition of parliament on a PR basis, and MPs who did not make it the first round are elected to correct party representation up to their proportion of the vote. The MPs elected in the first round are on the basis of a party list system, in which candidates are ranked on the basis of their popular vote.

If the MPs are split as equal numbers on both systems, it is impossible for one party to win an outright majority. Consider the extreme case where a party wins every seat on the first round. They will not have any MPs in the second round, and will therefore end up with exactly 50% of the seats in parliament. Choosing the size of the second-round vote therefore constrains the maximum majority the winning party can attain. For purposes of an example, let us fix the first round at 100 MPs, and the second at 80 MPs. This means that a majority of 20 is possible to attain.

Example 

Let's consider a specific scenario to see how this could work (using Australian parties for purpose of example but with made-up numbers):

• Liberal: 30%, 40 seats; 20% used up electing MPs
  
• Labor: 47%: 60 seats; 30% used up electing MPs
  
• National: 8%, 20 seats; 5% used up electing MPs
  
• Green: 10%, 0 seats; 0% used up electing MPs
  
• Family First: 5%, 0 seats; 0% used up electing MPs

In round 2, we have 80 seats to distribute, based on the remaining votes:

• Liberal: 10%, 18 more MPs, total 58 (32% of parliament)
  
• Labor: 17%, 30 more MPs, total 98 (50% of parliament)
• National: 3%, 6 more MPs, total 26 (14% of parliament)
• Green: 10%, 17 MPs, total 17 (9% of parliament)
• Family First: 5%, 9 MPs, total 9 (5% of parliament)
  

The MPs in the second round are those who had the highest vote out of the candidates who were not elected, ranked within their respective parties. Independents could be treated as a single party list in round 2; alternatively, they would have to form an alliance ahead of the election. This is a detail to work through.

Reflection on Example

We end up with something slightly off PR because we have allowed a theoretical majority of up to 20 for a party which won all the first round seats. However it is much closer to PR than you would have in the current electoral system in Australia which uses transferable preferences. RMPV also, unlike in a pure PR system, gives you not only a representative but also potentially multiple alternative representatives. If you are in an area where one party is very strong, the "alternate" may be quite far away -- for example, in a large rural constituency of a type the Nationals may dominate, you may not have a Greens alternate anywhere close enough to be practical to call on. However, in an inner-city area where several parties may have at least 5% of the vote, you may have several MPs to call on.

 

The RMPV result is not a bad outcome. If a community is fairly homogeneous in its composition, it makes sense to have a smaller variety of MPs representing their interests in parliament. There is however no dilution of their representation: all their votes have contributed (give or take the effect of fewer MPs on the second round than on the first).

Further evaluation of the idea would be useful: working up a range of scenarios to make sure that bizarre or pathological outcomes are not possible.