A guide to proportional representation, AV & STV

Why are we talking about electoral reform now?

Ditching Britain's old-fashioned 'first-past-the-post' electoral rules for a more modern and inclusive proportional representation system is an idea that seems to resurface whenever it might help the Government. Gordon Brown first explored constitutional reform as a response to the MPs' expenses scandal last year. Now Labour and the Conservatives are offering Nick Clegg electoral reform in return for Liberal Democrat backing in a coalition government.

What are Labour offering?

An immediate change to the 'alternative vote' electoral system followed by a referendum on a change to proportional representation.

What are the Conservatives offering?

A referendum on a change to the alternative vote system.

But isn't there much to be said for the current system?

The great advantage of first-past-the-post is that it produces clear winners and losers. Since each constituency produces an outright winner, even if by a single vote, there's more chance of producing decisive election results and hence governments with a clear mandate to rule. (They can then be thrown out just as sharply.) But first-past-the-post tends to magnify the power of the big parties. In 1983, for example, the Liberal/SDP Alliance received 25.4 per cent of the vote, a mere 2 per cent less than Labour; yet it won just 23 MPs while Labour got 209. And that points toa grave disadvantage of first-past-the-post – the fact that most of our votes are 'wasted'.

How are they supposed to be 'wasted'?

First-past-the-post doesn't care who comes second, still less third, which means that in most areas of the country with safe seats, you may as well not bother to vote. There are many Tory voters in Scotland, for example, but as they form the minority in each constituency, Scotland has just one single Tory MP. As a result British general elections pivot on the 200,000 or so voters in a handful of marginal constituencies who effectively decide the whole thing. Those arguing for PR cite this as a major reason for low turnouts at general elections.

What does proportional representation involve?

There are lots of PR systems - the Electoral Reform Society's preferred option is the 'single transferable vote', whereas Labour and the Tories are offering Nick Clegg the alternative vote. Both of these systems involve voters ranking the candidates in an election by preference. The systems differ in the number of candidates each constituency returns to parliament, with STV returning a number based on the proportion of each party's vote, and AV returning only one - still taking into account people's second, third etc.. preferences.

Why use proportional representation?

The aim is to reflect the plurality of opinion within a constituency. For this purpose constituencies tend to be much larger than those used for the House of Commons, and they return not one but several MPs - reflecting the relative share of party support in the area. By thus taking account of the spread of voter preferences, the problem of the wasted vote is minimised. It also makes it easier for smaller parties and independent candidates to get a foothold.

Does anyone actually use PR?

Most of the world's democracies and almost every single one of Europe's. Though PR may sound as boring as brown rice, countries going democratic for the first time - South Africa in the 1990s, or post-Saddam Iraq - almost always choose it. Proponents claim this has to do with its evident fairness. Cynics say it has more to do with the fact that PR tends to solidify the power of party bosses over their party's candidates.

Does PR solidify party control?

It often does in practice because party leaders like to operate on a 'closed party list' basis - meaning it's the leaders who determine the ranking of their party's list of candidates in each constituency, the voters just put their crosses by their preferred parties. So if a party - say Labour - then wins two out of the three seats up for grabs in a given constituency, the two chosen will be the two at the top of Labour's list. That's how it's done in elections for the European Parliament, for example. In PR systems that use open lists, on the other hand, voters vote for individuals standing for the different parties and so have a say in which candidates get to parliament. To that extent the electorate has a closer connection to its MP than it does under Britain's first-past-the-post system, where, for all the talk of the MP/constituent relationship, voters think in terms of party rather than candidate.

How do PR-elected governments differ from first past the post ones?

Since PR throws up more diverse parliaments, governments tend to be made up of coalitions - with all the problems, and some would say benefits, that entails: furious horse-trading between possible allies; compromises that bear scant relation to the manifesto commitments made by any single party; and failure to agree (in 1990s Germany a huge majority of the electorate and MPs agreed tax reform was necessary, but when it came to the details, no coalition could reach consensus). PR systems can also give rise to 'king-making' parties that wield disproportionate influence due to their ability to make and unmake coalitions (think of extremist religious parties in Israel, say). Having said that, Nick Clegg is something of a kingmaker, following our recent first past the post election.

But it still gives a 'fairer' result?

Perhaps, but the main charge aimed at PR is that it encourages voters to believe a functioning government can be constructed out of their kaleidoscope of preferences, when in fact, politics is about choosing one path over another. "We declare war or we don't: we cannot declare an 85 per cent war on the ground that 15 per cent of the electorate are pacifists," as Matthew Parris put it in the Times. Indeed, as Kenneth Arrow showed with his 'Impossibility Theorem', for which he won the Nobel Prize for Economics in 1972, whenever more than two people are faced with more than three options, there can be no such thing as a rational decision reflecting the will of the people. In their various guises, electoral systems are all just ways of defying this fact.   ·