The Alternative Vote (AV) system seems at first sight to offer a plausible improvement over the current, very unrepresentative First-past-The-Post (FPTP) system.
However, various simulations run using the AVOTER simulation program suggest that in practice it would make little difference, producing a change of elected MP in just 22 out of 649 constituencies (not counting the Speaker's seat, which carries no votes and would not in this instance have changed MP).
At the same time, the expense involved in counting and re-counting voting papers, and the consequent delay in producing a result, is enormous. If the May 2011 referendum had decided (amusingly, by using a First-Past-The-Post selection system with only two alternatives!) in favour of AV, then almost nothing would have been achieved:
The AVOTER simulation results
Tables summarising the simulation results are included for the UK as a whole and region-by-region, and are then set out in more detail constituency-by-constituency for each national region in the UK, with the equivalent tables for AV and ProFirst results being accessible by clicking the appropriate "ProFirst" or "AV" button in the index.
Changes in the MP elected under AV compared with First-Past-The-Post or ProFirst are highlighted in the tables - for instance in the Edinburgh South constituency.