So here's a modest proposal to get us back on track.
First, we cut the Official Cash Rate to 2%, the same level as the Australian policy rate. Nice big demonstration effect right there, with a 0.5% move instead of the usual 0.25%, plus it would be a genuine surprise (the futures market has only one 0.25% cut in the pipeline).
Second, we signal we'll match any future cuts in the Aussie rate (the futures market figures the RBA will cut by 0.25%, some forecasters think there are two cuts on the way).
Third, we do some quantitative easing (QE). The RBNZ buys enough government stock to drive down our current 10-year yield (3.04%) to the level of its Aussie equivalent (2.40%). It would help if Treasury cancelled its scheduled bond tenders and instead placed Treasury bills direct with the RB.
At that point, no sensible investors will pick New Zealand over Australia (the Aussies have a slightly better credit rating, so if the interest rates are the same, you'd pick them). Investors in New Zealand will clear off, and the currency will depreciate. It wouldn't hurt to give it a judicious nudge with some thin-market currency intervention.
If that doesn't get us nearer 2%, well maybe Vernon's right, and nothing ever will, but we'll never know unless we give it a go.
Course, the Auckland housing market will have turned incandescent, but you can't have everything, can you?
More seriously, I can't help feeling that it's theoretically possible, in the current collapsing-commodity, competitive-devaluation, out-QE-the-other-guy world, that there may be no feasible or desirable setting of local monetary policy that is consistent with 2% local inflation.
I've had a go in the past at trying to put this into some kind of formal framework (if you don't mind some simple graphs). My conclusion back then was that, if there was overseas monetary policy loosening (and a great deal more has happened since I wrote in 2013), and the RBNZ wanted looser policy but would prefer if it didn't exacerbate the housing market, then something had to give:
the Bank's got a bit of leeway: it doesn't have to keep inflation strictly at 2%. It's got a band of 1% to 3% to work with (on average aiming at a longer term average of 2%). Where the logic of things leads you to, though, is this: in current markets, the Bank will need to use this leeway, and let inflation undershoot 2% for some time.It's possible that the sub-2% undershoot that we have indeed experienced isn't such a bad result, in the round. It could be the best we could realistically achieve in current world market conditions - or at least the best we could achieve short of having slavering buyers stampeding from auction to auction to snap up the last house under $3 million.