Guesstimate of Election Result Under STV

In the wake of the recent BC election, a number of people have asked us what the result might have looked like if we’d been using the Single Transferable Vote that the BC Citizens’ Assembly had recommended.  While it’s always somewhat presumptuous to make such a prediction (mainly because people would likely vote differently (more honestly) under STV than they would under our current system where they have to make many tactical calculations, often voting for the person or party they think might defeat the one they like least rather than the one they actually favour most), we believe it is reasonable to ask for an educated guess.  At the bottom of this page, we describe our calculations/estimations in detail, but the basic assumptions we used are the following:

  • The STV electoral districts would be the ones defined by the Electoral Boundaries Commission in 2008
  • Voters would continue to cast first preferences for the same parties/candidates they voted for this time
  • Voters would transfer their ballots to another candidate of the same party as their top choice before anyone else
  • Voters who support the Conservative Party are much more likely to support a Liberal candidate than an NDP candidate
  • Voters who support the Green Party are somewhat more likely to support an NDP candidate than a Liberal candidate

With these caveats, the maps below illustrate our estimate of what the recent election might have resulted in had we been voting with STV.  The main points to notice are:

  • There are no regional ‘sweeps’ – both major parties have seats in all parts of the province (eg, the NDP in the Okanagan and Fraser Valley, the Liberals on Vancouver Island and the North Coast)
  • The seat counts for the NDP and the Liberals are closer to each party’s vote count (the Liberals have 46 seats, down from 50 in the real election, while the NDP are up from 33 to 36)
  • The Greens would likely have won a second seat in southern Vancouver Island, but did not have enough support to win elsewhere
  • The Conservatives did not have enough strength to win anywhere (though they were close in the Okanagan and Fraser Valley)
  • Vicki Huntington would still likely have won her seat;  other independents came close and might have had a chance at winning under STV

Note: the image below is ~2MB and may take a few moments to load.
2013_smp_vs_stv_-_long_banner

Methodology:

To arrive at our estimates, we combined the vote results by party from the preliminary vote tables from the 2013 election published by Elections BC. For each electoral district, we calculated the quota, which is the total number of valid votes divided by the number of seats, plus 1. We then calculated how many quotas were won by each party. We assumed that a party would win at least as many seats as full quotas they received (eg, if a party won 2.31 quotas, we would assume that that party would win at least two seats). For the last seat or two in each district, we judged which party would likely win the final quota. For example, if one party had 2.78 quotas and another had 1.31, we would presume that the first party would win three seats and the second only one.
We reiterate that this approach is only intended to give some rough sense of how an election might play out under STV, rather than being a specific prediction of how this particular election would have ended up. We have no way of knowing exactly how voters would have responded had they been able to vote more honestly (i.e., free of tactical considerations) in the recent election.

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