Domestic violence, mainly against women and children, kills far more people than wars and is an often overlooked scourge that costs the world economy more than $8 trillion a year, experts said.

The study, which its authors said was a first attempt to estimate global costs of violence, urged the UN to pay more attention to abuse at home that gets less attention than armed conflicts from Syria to Ukraine.

"For every civil war battlefield death, roughly nine people are killed in inter-personal disputes," Anke Hoeffler of Oxford University and James Fearon of Stanford University wrote in the report.

From domestic disputes to wars, they estimated that all violence worldwide cost $9.5 trillion a year, mainly in lost economic output and equivalent to 11.2 per cent of world gross domestic product.

In recent years, about 20-25 nations suffered civil wars, devastating many local economies and costing about $170 billion a year. Homicides, mainly of men unrelated to domestic disputes, cost $650 billion.

But those figures were dwarfed by the $8 trillion annual cost of domestic violence, mostly against women and children.

The study said about 290 million children suffer violent discipline at home, according to estimates based on data from the United Nations Children's Fund (UNICEF).

Based on estimated costs, ranging from injuries to child welfare services, the study estimated that non-fatal child abuse sapped 1.9 per cent of GDP in high income nations and up to 19 per cent of GDP in sub-Saharan Africa where severe discipline was common.

OVERLOOKED PROBLEM

Bjorn Lomborg, head of the Copenhagen Consensus Centre which commissioned the report, said household violence was often overlooked, just as car crashes attracted less attention than plane crashes when many more died in road accidents.

"This is not just about saying 'this is a big problem'," he told Reuters. "It's a way to start finding smart solutions." The centre draws on work by more than 50 economists, including three Nobel Prize winners, and looks at cost-effective ways to fight everything from climate change to malaria.

The study is meant to help the UN design targets for 2030 to succeed Millennium Development Goals set for 2000-15 that included curbing poverty and improving water supplies.

The new goals could include an end to severe beatings as an accepted form of discipline for children, for instance, or reducing violence against women at home.

The new cost estimates were based on previous US research that put the average cost of a homicide at $9.1 million, including lost earnings and costs to the justice system. The study then extrapolated those costs to other countries based on their GDP - a life would be valued at $910,000 in a nation where per capita GDP was a tenth of Americans'.

For non-fatal violence against women and children, the report based itself on US studies estimating that violent assaults each cost about $95,000, from medical costs to losses of income. - Reuters