The bank has every confidence that headline CPI inflation will get back into the target zone soon, when the impact of the steep drop in global oil prices falls out of the annual numbers.
But that is not the whole story. Non-tradables inflation is weak too, both by historical standards and relative to the bank's projections.
Non-tradables inflation reflects what is happening in the domestic economy, and in particular the labour market.
The puzzle there has been that the current surge in net immigration has not been anything like as inflationary as previous episodes would have suggested.
The conventional wisdom based on past experience is that net immigration - which includes the coming and going of New Zealanders as well as immigrants in the popular sense - boosts both the demand and supply sides of the economy, but that the effect on demand is felt sooner.
So all else being equal, the impact on net demand from a migration-driven rise in population will put upward pressure on wages and prices.
But this time we haven't seen that, or so the central bank argues.
If you compare the situation to that which followed the previous peak in net immigration in 2003, the differences are stark.
Non-tradables inflation through the mid-2000s was running around 4 per cent a year.
In 2015 it was 1.8 per cent, a 14-year low, and the bank forecasts it to get lower still over the first half of this year.
Headline inflation in the mid-2000s wobbled around the top of the 1 to 3 per cent target band, not 0.1 per cent.
Labour force growth was running at similar rates to what we have seen over the past couple of years.
But the composition of the increase was different in the mid-2000s, with more coming from natural increase in the population and less from migration.
There was a somewhat higher contribution from increasing labour force participation (the proportion of the working age population either employed or actively seeking work).
And nominal wage growth was stronger.
Research the Reserve Bank released last week looks for the differences between then and now that might explain why the current migration surge has proven so much less inflationary.
Over the past two years the number of people employed has grown by 112,000 or 5 per cent but most of that increase was met by growth in the labour force - 98,000 or 4 per cent - resulting in only a modest decline in the unemployed, down 14,000 to 133,00 over the same period.
The bank has unveiled a more nuanced indicator, dubbed "Luci", of how tight or loose the labour market is relative to a long-run average. It combines 17 labour market indicators, weighted so as to provide the best historical fit to the broader economic cycle.
During the mid-2000s boom labour market conditions were tighter than usual, Luci says, but they plunged deep into slack territory when the global financial crisis hit and did not get back into balance until 2014.
"With labour market conditions broadly in balance since 2014 there has been little upward pressure on wages recently," Bascand said.
We had noticed.
It doesn't help that labour productivity growth has been weak, averaging 0.8 per cent a year since the GFC, and just 0.3 per cent in the most recent year (to March 2015) for which we have data.
Over the 20 years to 2015, labour productivity growth averaged 1.4 per cent a year.
The Reserve Bank also points to changes in the drivers and composition of the net migration inflow.
Of the various factors which can influence migration flows, the bank's analysis concludes that the predominant driver in the current cycle is the weakness of the Australian labour market, reflected in a relatively high unemployment rate.
This discourages New Zealanders from crossing the ditch and means that more come home. That boosts the labour supply here.
In the year to February 2016 there was a net inflow of 1600 migrants from Australia, compared to an average net loss of 24,000 a year over the previous 10 years.
"Higher net immigration due to a higher Australian unemployment rate corresponds to a higher unemployment rate in New Zealand, whereas higher net immigration for other reasons reduces unemployment in New Zealand," Reserve Bank economists Jed Armstrong and Chris McDonald conclude.
There are signs the Australian labour market is improving, however. Employment growth was stronger than expected last year and the Reserve Bank of Australia expects it to remain strong enough to reduce the unemployment rate further.
It was 5.8 per cent in February.
Another factor is that the migrant inflow into New Zealand has been younger this time, with roughly twice as many aged between 17 and 29 as in their 30s and 40s.
In particular, there has been a marked increase in those arriving on student visas over the past two years, following a change in regulations in late 2013 allowing foreign students to work part-time.
Bascand said the bank's research found younger migrants had a smaller impact on inflation and house prices than older migrants. "This is probably because younger migrants arrive with fewer financial assets, spend less, and are less likely to purchase a house."
112,000 More people employed, past two years
98,000 Increase in the labour force
14,000 Fall in the number unemployed
Debate on this article is now closed.
