The chances of owning a home are slipping away for many Australians, as soon fewer than half of adults will own their own home, says one of the nation's largest household surveys.

Key points: 17,000 have been answering questions for 15 years

17,000 have been answering questions for 15 years More than two-thirds have relied on welfare at some stage over the last decade

More than two-thirds have relied on welfare at some stage over the last decade 77 per cent of children under the age of four never been to the dentist

The survey also said couples over 65 were Australia's wealthiest.

For 15 years the same 17,000 Australians have been answering questions about their income, savings, family life and health.

Their answers help to form a national snapshot, released annually in the Household, Income and Labour Dynamics in Australia Report (HILDA).

Professor Roger Wilkins, the report's author and an economist at the University of Melbourne, said they had been building up a "very comprehensive picture of how people's lives evolve over time".

He said a stand-out finding this year was that home ownership was going backwards.

"We're very soon going to have less than 50 per cent of adults who are home owners on current trends."

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Older homeowners reaping the rewards

Professor Wilkins said couples over the age of 65 who had invested in the property market were now reaping the rewards, and were considered the richest Australians.

"House price growth has been very strong," he said.

"In real terms house prices have gone up over 90 per cent for the period since 2001.

"Older households are much more likely to be home owners and also to own investment properties as well.

"Wealth has grown very strongly for older Australians, particularly those aged 65 and over.

"Since 2002 their average levels of wealth have grown in real terms by over 60 per cent."

Youth Action New South Wales chief executive Katie Acheson hoped the report would prompt urgent talks on housing affordability.

"As the prices increase, the entry point into the market is basically slipping away," she said.

Ms Acheson said policy makers needed to address issues such as negative gearing and capital gains tax.

Children less and less likely to visit a dentist

The HILDA survey suggested that housing affordability was just one of many pressing concerns for Australian families.

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The report said up to a quarter of single parent households are living in poverty, more than two-thirds of Australians have relied on welfare at some stage over the last decade, and 77 per cent of Australian children under the age of four have never been to the dentist.

Australian Dental Association president Dr Rick Olive said the findings were a concern.

"This is a consistent finding and if those children are never going to the dentist, we shouldn't be surprised that 48 per cent of five-year-olds are turning up with [tooth decay] in their primary or permanent teeth," he said.

"And 56.6 per cent of six-year-olds have cavities in their primary or permanent teeth."

So parents can add the dentist bill to the rising cost of child care.

The HILDA survey also said spending on day care and preschool care was up by 110 per cent since 2001.