Family breakdowns cost New Zealand at least $1 billion a year, a study by the New Zealand Institute of Economic Research suggests.
The figure of $1 billion was arrived at by calculating extra demand for government benefits and the cost of dealing with crime.
The 24-page report, commissioned by lobby group Family First, says the study is not aimed at criticising family types but understanding the social costs.
Author Patrick Nolan says more research and debate on family breakdowns is needed.
Dr Nolan says such research could look at tax-benefit programmes and incentives for marriage and work.
He would like to see what the effects of the incentives would have on decisions for partnering.