Local polls

Since we have another episode of democracy coming on, there are starting to be more stories about polls for me to talk about.

First, the term “bogus”.  Two people, at least one of whom should have known better, have described poll results they don’t like as “bogus” recently. Andrew Little used the term about a One News/Colmar Brunton poll, and Nick Leggett said “If you want the definition of a bogus poll this is it” about results from Community Engagement Ltd.

As one of the primary NZ users of the term ‘bogus poll’ I want it to mean something. Bogus polls are polls that aren’t doing anything to get the right answer. For example, in the same Dominion Post story, Jo Coughlan mentioned

“…two independent Fairfax online Stuff polls of 16,000 and 3200 respondents showing me a clear winner on 35 per cent and 50 per cent respectively.”

Those are bogus polls.

So, what about the two Wellington polls cited as support for the candidates who sponsored them? Curia gives more detail than the Dominion Post.  The results differ by more than the internal margin of error, which will be partly because the target populations are different (‘likely voter’ vs ‘eligible’), and partly because the usual difficulties of sampling are made worse by trying to restrict to Wellington.

It wouldn’t be unreasonable to downweight the poll from Community Engagement Ltd just because seem to be a new company, but the polls agree the vote will go to preferences. That’s when things get tricky.

Local elections in NZ use Single Transferable Vote, so second and later preferences can matter a lot.  It’s hard to do good polling in STV elections even in places like Australia where there’s high turnout and almost everything really depends on the ‘two-party preferred’ vote — whether you rank Labor above or below the L/NP coalition.  It’s really hard when you have more than two plausible candidates, and a lot of ‘undecided’ voters, and a really low expected turnout.

With first-past-the-post voting the sort of posturing the candidates are doing would be important — you need to convince your potential supporters that they won’t be wasting their vote.  With STV, votes for minor candidates aren’t wasted and you should typically just vote your actual preferences, and if you don’t understand how this works (or if think you do and are wrong) you should go read Graeme Edgeler on how to vote STV.