With the Referendum for AV coming up on May 5th, I wondered what effect the "Single Transferrable Vote" would have had on the 2010 election. So I got the election data from the Electoral Commission (http://www.electoralcommission.org.uk/elections/results/general_elections), and simulated an AV election...

You can draw your own conclusions from the results...

Assumptions

Obviously I had to make some assumptions, so I ran the simulation three times, with different assumptions.

I rated the political parties Left/Right wing on a scale of 1 (very Left Wing) to 5 (very Right Wing), so that (and you can argue with this...) Labour = 2, Lib Dems = 3, Conservative = 4. I made educated guesses for all the other parties, and may have got this wrong for some. I gave Independents a "flat" rating - which made them equally loved (or hated) by every persuasion.

Election 1 - Similar politics, votes transferred by proportion of vote

In other words, I tried to share the loser's votes with parties of similar politics. If there was more than one such party, they got the loser's votes by the proportion of their existing total vote. If there weren't any parties with similar politics, I went wider. This meant that when Lib Dems votes were transferred, most of the time they went by proportion to both Con and Lab. That probably won't happen for real.

Here's the result:

Election 2 - Similar politics, by proportion, except Lib Dems vote against lead party in each seat

So if Con are 1st, Lab 2nd, LD 3rd, with no clear majority, the LD votes will all go to Lab.

Election 3 - As above, but Lib Dems now only transfer to Labour

Who knows, it could happen?

Complete Results

Here's a PDF of my complete results - including how all the votes got transferred: AV Simulated Elections.pdf