The richest 1% of people now own half of all household wealth, according to a global report.
The Credit Suisse Research Institute's Global Wealth Report also found that someone needs just 3,210 US dollars (£2,105) to be classed as being in the wealthiest half of the world.
The report said that wealth inequality has continued to increase since 2008, "with the top percentile of wealth holders now owning 50.4% of all household wealth".
It predicts that the number of dollar millionaires worldwide could increase by 46% in the next five years, reaching 49.3 million by mid-2020.
The report looked at the wealth of 4.8 billion adults across more than 200 countries.
Across the globe, it estimates there are 123,800 ultra-high net worth individuals - defined as those with a net worth of more than 50 million US dollars (£32.8m).
Of these, 44,900 are worth at least 100 million US dollars (£65.5m) and 4,500 have assets above 500 million US dollars (£328m).
North America is home to around half of those with ultra-high net worth, while Europe is home to around one quarter.
In the UK, around 5,378 people are classed as being of ultra-high net worth, a figure which is up by 7.3% compared with 2014.
Michael O'Sullivan, chief investment officer, private banking and wealth management at Credit Suisse, said: "We are clearly in a growth industry, with wealth set to continue its upward trajectory.
"The number of dollar millionaires could exceed 49.3 million adults in 2020, a rise of more than 46.2%, with China likely to see the largest percentage increase, and Africa as the next performing region."
Mark Goldring, Oxfam GB chief executive, said the findings are "the latest evidence that extreme inequality is out of control".
He said: "Without action to tackle the growing gap between the richest and the rest, we have little hope of ending extreme poverty."
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