30 years is longer than one week

From Stuff, on the housing affordability index

“The university said a key driver was the median house price, which rose more than $30,000 over the year, eclipsing the $19.35 increase in average weekly wages.

Interest rates also rose from 5.51 per cent to 5.97 per cent on average.”

Comparing the median house price increase to the median (I think) individual weekly wage and salary income increase is a particularly opaque way of presenting the data. Obviously $30,000 is a lot more than $19.35, but one is paid over thirty years an the other is received over one week.

For example, it should be easy to say what increase in average weekly earnings would be necessary to not be ‘eclipsed’ by the $30,000 house price increase? If the report doesn’t say, the journalist should ask. The reader shouldn’t have to do that calculation. It turns out that if median weekly wages had risen $34.50 instead of $19.35, they wouldn’t have been eclipsed and the affordability index would have stayed constant. This isn’t the impression that you’d get from the story.

The argument for an affordability index is that it makes affordability changes easier to understand by reducing them to a single number.  That’s only true either if you understand how the number is calculated (which takes quite a lot of research) or you don’t really care exactly what it means.