The UK has FPP. The Conservatives won a majority with 37% of the vote. The Greens and UKIP got over 16% of the vote between them yet got only a seat each. This is seen as unfair, and proportional representation does produce more proportional results which many see as fairer.
The activism for proportional representation tends to come from the left, but I’m not sure they would have liked a proportional result on the 2015 election. I show below what it would have been.
Of course it is likely people would have voted differently under a PR system. Yes. But we can only model with the data we have, which is the actual result.
So under PR the UK Independence Party would have 83 seats, instead of one. The SDP would hold 31 seats instead of 56 and the Lib Dems 52 seats instead of eight. And the Conservatives and Labour would have fewer seats – and the Greens 25.
If you look at the blocs, the right bloc would still have a majority under proportional representation. They’d be just 10 seats down. However it would be a Conservative/UKIP Government, not a majority Conservative one.
The left would do worse under PR with Labour and the SNP both losing seats, but the Greens picking some up. They’d be 33 seats down compared to FPP.
The Lib Dems in the centre would be best – going from eight seats to 44.