The researchers compared levels of child labour and schooling across wealth groups in India, Peru and Ethiopia and found the richest groups in each country were healthier, and more skilled, than the average individual, and that this difference increased with income inequality.
Jayanta Sarkar and Dipanwita Sarkar, from Queensland University of Technology Business School, developed an innovative overlapping generations economic model to explain how child labour stubbornly persists despite falling poverty in developing countries.
Figures from The World Bank show the number of people living on less than USD 1.25 per day decreased from half the citizens in the developing world in 1981 to 21 per cent in 2010, despite a 59 per cent increase in the developing world population.
UNICEF estimates 246 million children are still engaged in child labour.
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Jayanta said the "fixed private cost" of schooling meant the poor had less access to education relative to the rich, a key driver in child labour among the poor.
"Instead of schooling, they invest in child health to ensure children possess physical capability to perform unskilled work," he said.
"There is a clear link between income inequality and intensity of child labour. But, more income does not always reduce child labour. In fact, as wages rise child labour rises in families who find schooling too expensive.
He said that banning child labour would actually end up hurting the poor as child income would dry up and as a result private investment in health would fall. A child labour ban had to be accompanied by an increase in access to education.
"The research finds a key connection between inequality of opportunity and children's human capital outcome, which means that even as incomes increase, child labour will remain without significant changes," he said.
The study was published in the Economic Inquiry journal.