The discussion over at Dim-Post inspired me to have a play with the New Zealand Election Study (NES) data.
Each wave surveys a fairly large sample of voters and a small sample of non-voters. So I was having fun, and I started to wonder what would happen if all the non-voters with a party preference had got out and voted on Election Day. There are a bunch of caveats to this analysis, including the small sample size and how representative the sample of non-voters was. BUT, if we assume for a moment that the data were broadly representative, then inspiring all non-voters to get out and vote wouldn’t have had a massive impact on the 2011 result.
I ran the same analysis on the 2008 data. A higher voter turnout would have made a bigger difference in 2008. The result for National would have been lower by around 4 points and the result for Labour would have been higher by the same amount (based on results for just 15
12 non-voters with a party preference)
There were a few odd things in the 2008 data – I couldn’t get the validated voter/non-voter result to match the actual voter turnout, and there seemed to be some sort of weighting issue (which I haven’t explored yet). If anyone has time to check that out and replicate the above, I’d appreciate it.
EDIT: Having thought more about it, the way I combined the results assumes that the small number of non-voters in the sample, without a preference, would vote in a similar way to those non-voters a preference, when they had ended up in the ballot box.