# Half of electorates above average

Last week, The Australian reported on the politics of same-sex marriage in the West Island. The story is a bit old (I picked it up from John Quiggin), but it’s such an impressive example that it’s still worth mentioning.

Roy Morgan Single Source survey data from the middle of last year shows that over a quarter of Australians aged 14 and over — 26.8 per cent — agreed with the blunt proposition “I believe homosexuality is immoral”.

That’s a fairly small minority, and although there is variation, it’s a minority everywhere in the country. But there is this:

In 80 of the 150 federal electorates, an above-average number of people support the proposition.

So. In about half the electorates the proportion supporting the proposition is above the national average (but still a minority), and in about half it is below the national average. That sure tells us a lot.

Thirty-three of these 80 are Labor seats. They take in a who’s who of the ALP.

Of the half that are above the national average, the proportion held by Labor is 41%, a little *less* than the 48% of all seats they hold.

Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »

Just in case some people don’t realise, it is worth pointing out that these statements aren’t always as stupid as they sound. If the mean and the median don’t agree, you might get more or less than 50% being below “average”.

An obvious example is when looking at the average wages. Because a few high earners really earn loads they inflate the average (mean) wage greatly leaving far more than 50% earning less than the average wage. It’s for this reason that Statistics NZ now focus on the median wage (the wage that 50% earn more than and 50% earn less than). House prices are another one where the mean and median are very different.

5 years ago

Yes, it’s certainly possible for statements about the proportion above the mean to be non-vacuous. In fact, you can have nearly everyone above the mean (number of legs, for example)

In these stories it’s the combination of the statement and the fact that there’s no reason why the number should be surprising or interesting.

5 years ago