Scottish, Welsh, German and New Zealand Parliamentary elections use a type of Proportional Representation called the Mixed Member Proportional system (MMP).
The ten-second definition of MMP is this:
We still elect local MPs. Voters unrepresented by the local results top them up by electing regional MPs. The total MPs match the vote share.
MMP is a voting system which mixes our winner-take-all system with an element of proportional representation, so that the number of MPs elected to Parliament from each province matches the share of the overall votes cast by supporters of each party in that province.
Different places use different MMP models. This is a description of an MMP model with “open lists.”
Each voter has two votes.
The local vote is used to elect an MP to represent your riding, as today.
The regional vote or party vote is used to elect several regional MPs from your region.
The local vote can be cast by marking your ballot with an X for any candidate standing in your riding, as we do today. The candidate chosen by the largest number of voters in a riding wins the seat on a winner-take-all basis.
The regional vote can be cast by marking your ballot with an X for any regional candidate standing on the regional ballot.
If that candidate is a party candidate, this vote counts as a vote for your party. The parties' regional votes are then counted to give the level of support for each party in the region.
If a party’s voters have managed to elect only a few local MPs in that region, or none at all, that party gets additional “top-up” seats to make their final total more in line with their vote share in the "top-up" region.
The party’s regional candidates with the most votes win those seats. That’s why it’s called “open list.”
Every voter has competing MPs: you can go to your local MP or one of your diverse regional MPs. Germans call this "personalized proportional representation."
Your ballot will look like this ballot that PEI voters chose in their referendum.
Here are further details on this model as designed by the Law Commission of Canada.
What would the 2015 election results have been under this model?
(The number of regional MPs you have depends on the size of your "top-up" region: if they are medium-sized regions it might be five, maybe as many as eight or more. In smaller provinces, the "top-up region" would be the whole province.)