Ghana could end child labour on cocoa farms by increasing the prices it pays impoverished farmers by about 50%, a U.S. study said, as global efforts to end child labour stall.

Paying just 3% more at the farm gate could stop children in Ghana doing the most hazardous tasks, like using machetes, or working more than 42 hours a week, researchers said, as the illegal practice is driven by poverty and rarely prosecuted.

“We figured there has to be some kind of incentive, on top of the laws, to get the farmers to stop using child labour,” said Jeff Luckstead, an agricultural economist at the University of Arkansas, co-author of the study in the journal PLoS ONE.

“It’s a really difficult issue because these are very poor farmers ... They don’t have many options - they can’t just go and hire people,” he told the Thomson Reuters Foundation.

A PLoS spokeswoman later added that while the underlying conclusions of the report were all accurate, some of the numbers cited in the study were under review with an update to follow shortly. No further details were given.

Ghana is the world’s second largest cocoa grower, with more than 700,000 children producing the crop, often doing dangerous jobs on family farms like carrying heavy loads or using sharp tools, the anti-slavery group Walk Free Foundation says.

Big chocolate makers have been under pressure to clean up their supply chains since reports of child labour on West African cocoa farms emerged in the 1990s, with major names like Mars and Hershey promising to only buy ethical cocoa by 2020.

The International Labour Organization has said the world is unlikely to meet a target of ending child labour by 2025, which is part of 17 global development goals agreed in 2015 at the United Nations.

Researchers came up with the price premiums by analysing data between 2003 and 2015, including household budgets, cocoa prices and production and children’s education and leisure time.

While recognising a 50% price increase was “implausible”, the study suggested that Ghana could become more competitive globally if it could certify its cocoa as “child labour-free”.

All cocoa produced in Ghana is sold to the regulator, COCOBOD, which paid farmers 7,600 cedi ($1,435) per tonne last year. Ghana exports almost 20% of global cocoa output of some 4.8 million tonnes a year.

Most cocoa farming families live below the World Bank’s poverty line of $2 a day, according to the charity International Cocoa Initiative (ICI), fuelling child labour.

But Genevieve LeBaron of Britain’s Sheffield University, who was not part of the study, said the key to ending poverty among cocoa farmers was not necessarily raising COCOBOD’s prices but fairer distribution of profits within the chocolate sector.

The global chocolate industry was worth about $85 billion in 2018, and is projected to jump to $102 billion by 2022, according to leading research firm Mintel.

"If you look at the annual profits of the largest cocoa and chocolate confectionary companies in the world, there's plenty of money in that supply chain that could be redistributed downwards along the value chain," said the politics professor.