There were 1,645 billionaires globally as of March 2014, according to Forbes data cited in the Oxfam report, up from 793 in March 2009.
Oxfam honed in on this figure to highlight the growing gap between the world's rich and poor. Hundreds of millions of people live in abject poverty without healthcare or education, while the super-rich continue to amass levels of wealth they may never be able to spend.
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The report 'Even it Up: Time to End Extreme Inequality' noted that the world's richest 85 people saw their wealth jump by a further $668 million per day collectively between 2013 and 2014, which equates to half a million dollars a minute.
In January Oxfam issued a report highlighting that the world's 85 richest people's collective wealth is equal to that the poorest half of the world's population.
"Far from being a driver of economic growth, extreme inequality is a barrier to prosperity for most people on the planet," said Winnie Byanyima, international executive director of Oxfam.
"Inequality hinders growth, corrupts politics, stifles opportunity and fuels instability while deepening discrimination, especially against women," she added.
The Oxfam report is the opening salvo of a fresh Oxfam campaign - Even it Up - which aims to push world leaders into helping ensure the poorest people get a fairer deal.
"Action is needed to clamp down on tax dodging carried out by multinational corporations and the world's richest individuals," the authors of the report added.
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Oxfam suggests a levy of 1.5 percent on billionaire's wealth over $1 billion would raise $74 billion, which would generate enough each year to get every child into school and deliver health care in the poorest countries.