But New Zealand's 36 per cent compares with 38 per cent in Canada and 28 per cent in the United States (as of 1998).
Retirement Commissioner Colin Blair said: "We knew there was quite a bit of investment in businesses and farms but we never had a figure for that before."
The survey estimates people have $38 billion invested in businesses and a similar amount in farms. Each represents about 9 per cent of households' total assets.
Blair is not about to give a simple, still less an affirmative, answer to the question: are we saving enough for retirement?
A lot more trawling through the data gathered by the household savings survey is needed, he says.
"For example, I would like to look more closely at the position of those over 50. How many are still paying off mortgages? What have they got in the way of financial assets?
"And if they haven't got much, what ability do they have to accumulate some in the last 10 years, say? Because that seems to be when a lot of people are banking on doing their real retirement savings."
Perceptions of what is "enough" income in retirement depend on what incomes people have enjoyed before, Blair says.
"People who have never had much in the way of income are probably resigned to the fact that New Zealand Super is it. Those who have had pretty good incomes through their working lives will be wanting quite a bit more."
The survey found that only 21 per cent of "economic units" - that is either single people or couples - are contributing to superannuation schemes.
The $25 billion they have in such vehicles sounds a lot but is only 6 per cent of total assets of $444 billion.
Life insurance policies with a surrender value represent a further $9 billion, shares $14 billion, managed funds $12 billion and other financial assets (such as bonds) $6 billion.
Only 2 per cent, both of single people and of couples, said their main source of income was investments. Even if all of them were retired, they would still be a small minority - 17 per cent of all single people are over 65 and 15 per cent of all couples.
The survey found that 4 per cent of single people over 65 and 7 per cent of couples still had mortgage debt, and not trivial amounts either - a median debt of $42,000 for the couples.
But this may be less alarming than it looks at first sight as it includes mortgages on all properties owned, including investment properties.
Altogether, mortgage debt is $54 billion out of a total household debt of $68 billion.
About 23 per cent of all single people and 8 per cent of couples have a negative net worth - they owe more than they own.
Among those aged 18 to 24, 40 per cent have student debt, at a median level of $10,000 for those who are single and $12,000 for couples.
Inland Revenue data indicates that the average amount borrowed in 2000 was twice the amount borrowed in 1992.
For both single people and couples aged 18 to 24, median net worth was negative for those with student loans but positive for those without. Those without a student loan are much more likely to have a mortgage than those with.
The survey covered 2392 single people and 2982 couples and was conducted between August and December last year. It cost $2.3 million.
But it provides a snapshot only. "Many questions raised by the data will only be answered by a repeat of the survey," Blair says.
He says this database will help policy advisers appraise the impact of compulsory retirement savings. "It would help answer such questions as, 'If we compel people to put away, say, 5 per cent ... what is that going to do to their ability to repay the mortgage or the student loan - all those other things'."
Graph: Median net worth by age
