It has a so-called "super-ageing" population - with more than a third of its people over 60.
But the first blast of New Zealand's 2018 census data confirms we're nothing like Japan.
The difference has to do with New Zealand's much more rapid rate of population growth in the past five years.
Japan's net migration rate is 0.56 people per 1000 people. Ours is 11.4 per 1000.
Westpac economists picked up on the drop in our median age in their latest quarterly economic report.
"New Zealand's workforce has seen significant growth in the 25-34 age group, which is where migrants (both inward and outward) tend to be concentrated," writes Westpac senior economist Michael Gordon.
"Indeed, the median age in New Zealand has fallen slightly in the last five years, counter to the global trend of an ageing population."
If a high proportion of these people remain in the country for the long haul, then it will have significant distributional impacts, he says.
"These people will bolster the workforce for decades to come."
In other words, concerns about how we're going to cover superannuation and retirement of the baby boomer generation might not be as bad as feared.
Gordon accepts the trend is far from clear-cut.
Japan has a 'super-ageing' population - with more than a third of its people over 60. Photo / 123RF
For example, the average age (as opposed to median) has continued to rise.
But that is happening at a much slower rate that previously assumed.
It's also still possible that the immigration cycle might turn sharply lower - but they might not.
Last week, I wrote about just how dramatically our population growth has exceeded expectations in the past 15 years.
In 2004, Statistics NZ forecast New Zealand's population would hit 5.05 million in 2050. In fact it will hit five million next year.
The obvious conclusion is that this has added to or housing shortage and infrastructure deficit.
But the closer you look at the numbers, the more complex the ripple effect is.
Population projections flow through many aspects of public policy setting.
Consider, for example, the headline-grabbing paper produced by Sir Michael Cullen's Tax Working Group in 2018.
It highlighted the deficit in tax take we'll face in the next decade or so because of the higher proportion of retirees.
"If the Government is to continue providing healthcare and superannuation at current levels, then the level of taxation will need to increase, or spending on other transfers or publicly provided goods and services will need to fall," the report said.
Sir Michael Cullen's Tax Working Group highlighted the tax deficit New Zealand will face because of the higher proportion of retirees. Photo / NZ Herald
But, of course, there is a third option - that our demographics don't follow expectations.
The Tax Working Group paper was based on estimates done by Stats NZ in 2016 for a 50-year outlook
By 2016, Stats NZ had upgraded its expectations for long-term average net migration gain from 10,000 (used in the 2004 forecast) to 15,000.
It forecast a median age of 40 years is likely to be reached by the early 2030s.
It would be a brave pundit that picks that we won't see some sort of cyclical dip in the next decade.
But the longer the rate of net migration stays ahead of 15,000 per year, the less likely the it is that 2016 assumptions will hold true.
As well as the base case, projections by Stats NZ include a range of scenarios.
The 2016 projection included a high-migration scenario. That assumed an average net gain of 30,000.
Yet we've actually averaged a net migration gain of around 55,000 gain for the past five years.
So when you look at expectations to the 2030s - which is when we've previously expected we'll have to start drawing on the New Zealand Super Fund - we are already so far ahead of the curve that our long-held assumptions must be in need of another look.
I'm no statistician. There will be those that argue New Zealand's immigration cycles have always been quite dramatic.
We could see a sudden plunge and the ageing of the population may well resume.
It is a judgement call as to how much New Zealand's migration rate has shifted at a structural level, as opposed to just being a larger and longer cycle than usual.
I've argued for the former. New Zealand's place in the world is far more prominent than it once was.
Stats NZ's website says it wil produce a new set population projections, based on the 2018 census, in June next year.
It will be fascinating to see how much the demographers think the goalposts have shifted and what the policy response from our government agencies will be.
New Zealand is not Japan, not by a long shot.
We have a massive baby boomer retirement to deal with. But we're also going through an immigration-led demographic shift of historic proportions.
