It says something about this Government's sense of urgency on housing affordability that it has taken five years to develop a measure that is two years out of date.
The official index announced this week subtracts the cost of housing (buying or renting) from a renting household's income. It then compares the money left over to a national median figure in 2013, called the national affordability benchmark.
The current threshold is $662 per week for a one-person household, with an extra $331 for each adult and $199 for each child.
The latest available data for would-be buyers shows 81 per cent of households in New Zealand and 86 per cent in Auckland fell below this line in June 2015. Unaffordability for renters was 66 per cent nationally and 64 per cent in Auckland.
At first glance the index looks like a new way of telling us what we already know. The nation has a regular stream of house price data and two well-established housing affordability indexes from interest.co.nz and Massey University.
Only last month the interest.co.nz index found that it now costs a typical young first-home-buying couple half their after-tax income to pay off a mortgage on a modest Auckland house.
This figure, which sums up the problem well from a frustrated buyer's perspective, has been tracking upwards for years despite Government claims of action.
It is natural to wonder whether the new measure could be a smokescreen to throw critics off the scent but there are clearly several points in its favour.
After a year of testing it will become one of the Government's primary statistical measures, which means housing affordability should be taken more seriously. (As child poverty campaigners have discovered, it is difficult to argue for change if you cannot start with a definition of the problem.)
Covering about a third of the population, it is more accurate than the existing indexes because it measures real incomes instead of averages. Like interest.co.nz, it sensibly assumes first-time home buyers are looking for a relatively cheap home in the bottom quarter of prices.
More dangerously it assumes that they will buy in the area they are renting, which might be reasonable for parts of the country but not Auckland. It gives a reliable comparison with renting costs and the time lag will gradually drop to six months.
However, the new measure still has its drawbacks. It makes no attempt to measure the time it takes to save for a deposit, which remains a serious obstacle to buying, especially in Auckland.
And while the results look grim, it is debatable whether this is the best way to measure whether people can afford to buy a house. Some of those who fall below the benchmark may still decide to buy, so the figures do not necessarily prove that 81 per cent of renters are locked out of the market (a claim likely to be heard frequently in election year).
The new housing affordability measure will be most useful in showing changes in the months and years ahead.