The 2015 election under 3-4 member Single Transferable Vote
When I worked for the Electoral Reform Society I rather enjoyed getting paid for working out what election outcomes might have been under alternative electoral systems. In these straitened times, I seem to be doing it for free as a sort of loss-leader, but this I guess is the way the economy in general is going, so if anyone wants to commission fuller workings, please get in touch…
I am well aware that modelling the consequences of different electoral systems is at best an approximate art. Parties behave differently, in the number of candidates they stand and the way in which they target their efforts. One also has to make up imaginary constituencies or regions to serve as electoral units, which again can affect voting behaviour. Voters also think differently – they are relieved of the tactical considerations that affect voting in First Past the Post (FPTP) and this makes the ‘squeeze’ message (only party X can defeat party Y here) much less effective. Incidentally, anyone who thinks FPTP is simple should have a look at this Daily Mash article…
The model result here is using the Single Transferable Vote (STV) in constituencies returning 3 or 4 MPs each. This if the form of proportional representation introduced for Scottish local elections in 2007 and used for all Northern Ireland elections except Westminster. It is pretty simple from the voter’s point of view – you rank the candidates in order of preference, including quite often the ability to choose between more than one candidate of a larger party – and the (quite elaborate) counting system means that few votes fail to have an influence on the outcome. 3-4 MPs per constituency is a pretty low-end version of proportionality; the larger the number of people elected from the constituency, the more chance there is for smaller parties to gain seats and the more the result will resemble the votes cast. I was somewhat surprised with how proportional even this limited version of PR would have been in 2015.
The STV constituencies are illustrated in the coloured map. The colour scheme is entirely arbitrary and is there solely to differentiate the constituencies from each other. Orkney & Shetland and na h-Eileanan an Iar are treated as single-member constituencies. I have added existing constituencies together, but if this reform ever happened new constituencies would surely be created based on more coherent units.
(ADDED PARAGRAPH AFTER EDIT) One also has to consider the impact of second and lower preferences on the result. Real-world experience suggests that preference flows are neither as complete nor as clear as is often implied by such models, so this has been deliberately cautious with assuming much about preferences. Broadly, for the cognoscenti of STV, seats are awarded for every whole quota’s worth of support for a party, and then for anyone with more than 80 per cent of a quota. Preferences flows among the remainder are assumed to have small net effects – most Greens in England and Wales going to Labour, in Scotland to SNP; a weak but present unionist preference ordering in Scotland; UKIP votes splitting weakly Conservative in Con/Lab choices and strongly Conservative in Con/LD choices. There may be room to revisit the assumptions when further study has revealed more about preference orders, but the effect of different assumptions is pretty small as most seats are awarded either on whole quotas or large shares of quota that would require implausibly strong adverse transfer patterns to overcome.
The model outcome in seats nationally would be Conservative 280, Labour 241, UKIP 38, SNP 37, Lib Dem 29, Plaid Cymru 4, Green 2, the 18 Northern Ireland seats and the Speaker. In proportions of the whole House this would give the Conservatives 43 per cent of seats for 37 per cent of the vote, Labour 37 per cent of seats for 30 per cent of the vote, UKIP 6 per cent of seats for 13 per cent of the vote, Lib Dem 4 per cent of seats for 8 per cent of the vote and SNP 6 per cent of seats for 5 per cent of the vote. 3-4 member STV therefore would have a significant bonus for the leading two parties (and for the SNP in Scotland) while giving adequate representation to the Lib Dems and UKIP who were ill-served by FPTP. It would not help the Greens all that much, but this may be masked by the greater willingness of voters to support the Greens in a reformed system. One perhaps significant finding is that, surprisingly, UKIP would not elect any MPs from the South West on this model despite the region being one of its stronger areas in many past elections. It may be that there was a late switch from UKIP to Conservative by many voters in this region in particular, and that this would not necessarily happen if the electoral system were different.
The effect of even a modest degree of proportionality in the electoral system on the main parties would be to redistribute their support around a bit – the metropolitan areas would not be devoid of interest to the Conservatives, and Labour would have more representation (commensurate with its vote) in southern England.
When I first posted the headline number on Twitter, someone asked me ‘what sort of government would that produce’? A fair question. My guess would be a Conservative minority with occasional support from the Ulster Unionists (DUP and UUP), UKIP and the Lib Dems, and a measure of passive toleration from the SNP. It might be an easier show to keep on the road than a triumphalist yet divided Conservative majority, but that is even more speculative than any of these calculations.