New figures show there are 13 million spare bedrooms in Australia despite the massive rental crisis.

The Survey of Income and Housing figures show two-thirds of those rooms are in houses with only a couple or a single person living in them.

It predicts the number of “vacant” rooms will continue to rise as a result of Australia’s ageing population holding on to “empty nests” with little incentive to downsize.

The Centre for Independent Studies chief economist Peter Tulip says changes to stamp duty could relieve some of the financial disincentive to downsizing.

“Tax on [property] turnover means people are in houses that don’t suit their circumstance,” he says. “So, we would get a better allocation of houses if we replace stamp duty with land tax.”

He says removing the family home exemption from the aged pension asset test could also help.

Demographics Group’s Simon Kuestenmacher says many delay downsizing because they prefer to age at home rather than enter aged care.