What is Giving Compass?
We connect donors to learning resources and ways to support community-led solutions. Learn more about us.
Some 82% of money generated last year went to the richest 1% of the global population while the poorest half saw no increase at all, the charity said.
Oxfam said its figures - which critics have queried - showed a failing system.
It blamed tax evasion, firms' influence on policy, erosion of workers' rights, and cost cutting for the widening gap.
Oxfam's report is based on data from Forbes and the annual Credit Suisse Global Wealth databook, which gives the distribution of global wealth going back to 2000.
The survey uses the value of an individual's assets, mainly property and land, minus debts, to determine what he or she "owns". The data excludes wages or income.
The methodology has been criticised as it means that a student with high debts, but with high future earning potential, for example, would be considered poor under the criteria used.
But Oxfam said even if the wealth of the poorest half of the world was recalculated to exclude people in net debt their combined wealth was still equal to that of just 128 billionaires.
Read the full article on the wealth gap by Katie Hope at BBC