At present, the UK uses the ‘first past the post’ system to elect MPs to the House of Commons. Should the ‘alternative vote’ system be used instead?
The "first past the post system" is simple to understand - each voter casts his ballot for his preferred candidate (in practice, this is usually the candidate nominated by the preferred PARTY). These are added up and the winner is the person who has got more votes than any other candidate.
The system worked well when Britain had an essentially two-party system. (Even then, anomalies could result - in 1951, where all but 9 seats were shared between Labour and the Conservatives (the Ulster Unionists and National Liberals sat with the Tories) - the popular vote was
Labour - 13,948,385 (48.8%) Conservative - 13,717,850 (48.0%)
yet the Labour Party lost its Commons majority, and was thrown out of government. The Tories won 51.36% of the seats, and gained a Commons majority of 17.
Now with a multi-party system the possibility of a party taking charge of government with a minority of votes is theoretically possible - and in fact Tony Blair won his massive Commons majority of 179 with just 43.21% of the popular vote [but 63.43% of the seats in the House of Commons]. The winner in any seat just needs to get 1 more vote than any other candidate.
Many suggestions have been made to overcome the effect of this. There are TWO different types of system possible -
Majoritarian (sometimes called 'Plurality Voting Systems') - these type of methods are based on the idea that the elected official should be 'representative' in the sense that they have secured the widest support from the electorate. In 'First Past the Post' the person who wins more votes than anyone else wins. In "AV" the winner is the person who gains the greatest number of preferences (their own 1st preference votes plus 2nd (and if necessary 3rd and so on) preferences of candidates who have been eliminated). The winner must have 50% or more of positive preferences. Majoritarian systems do disadvantage groups that are unable to reach out from their base - extreme groups or ethnic groups for example.
Proportional - these methods of voting begin with a wholly different philosophy - they allocate seats in a parliament on the basis of what proportion of the total vote a particular group can gain - irrespective of whether they are able to attract 'outsiders'. AV is NOT a proportional system.
So which is 'best' or 'fairer'? That of course depends on a vital value judgement. Is acceptability and inclusiveness more important than the right to have someone represent you who shares only your views? Is simplicity in voting a greater good than acceptability to the greatest number of the electorate?
Smaller parties gain from proportional systems. 'First Past the Post' can deliver the reins of government to a cohesive group able to divide and conquer its opponents. AV will allow the general preferences of the electorate to triumph (if you assume that Britain is essentially a social-democratic country (quite an assumption!) - then centre-left governments are more likely than Conservative governments.
There is a lot of academic material on the impact of different voting systems (try a google scholar search!) - but also a guide from the Electoral Commission on the referendum - available here.
Link to Yes Campaign Link to No Campaign
