Yes, the outworkings of a multi-seat constituency single transferable vote system can be quite complex if you want to maximise your seat/vote ratio, but I am always amazed at the degree to which they are understood even by non-political people. The vote count itself can extend to over two days as the votes of eliminated candidates have t be re-counted to see who the next preferred candidate on a ballot is.

It also has a significant effect on political culture, as few candidates get elected on the strength of first preferences alone. All candidates and parties therefore seek to be as "transfer friendly" as possible and avoid insulting or sharp ideological exchanges with their opponents, as these tend to turn most voters off. This has an overall moderating effect on discourse and you don't get quite the extremes you get in some European countries.

N. Ireland is an interesting real world laboratory experiment in the effect of voting systems because Westminster Elections are still held on the basis of single seat, first past the post elections while the same constituency boundaries are used for 5 seat constituency NI Assembly elections (due next month). The first system tends to favour the big sectarian parties while the STV system enables the non-sectarian Alliance party and smaller parties like the Greens and socialists pick up the odd seat in more diverse constituencies - generally in later counts due to the transfer of lower preference votes.

It is getting to the stage where Alliance can challenge all the major parties and pick up seats even in Westminster elections, but it would never have been able to develop that electoral base without its success in local and Assembly elections. I will do a diary on it soon, but at the moment its still all to play for, with the odds being that Sinn Fein will displace the DUP as the largest party and become entitled to the First Minister role, a hugely significant symbolic blow to unionism, even if it means little in practice, as the First and Deputy first ministers can only act in concert.

Index of Frank's Diaries