And, most likely, that first trillionaire would be Microsoft co-founder Bill Gates .

In our lifetimes, we could see the first trillionaire.

The report also finds that, given the exponential growth of existing wealth, the world could have its first trillionaire in the next 25 years, when Gates would be 86.

When Gates left Microsoft in 2006, his net worth was $50 billion, according to Oxfam. By 2016, his wealth had increased to $75 billion, "despite his commendable attempts to give it away through his Foundation," the report says.

In addition to the charitable work Gates does through his personal foundation, he is one of the founding members of The Giving Pledge, a commitment from some of the richest individuals in the world to give away more than half of their worth.

For the hypothetical analysis, Oxfam researchers apply the average rate of growth the ultra-rich have been enjoying, 11 percent per year since 2009, to Gates' current levels of wealth (over $84 billion, according to Forbes). If his investments keep doing as well as they have been, the 61-year-old Gates could indeed become the world's first trillionaire.

"In such an environment, if you are already rich, you have to try hard not to keep getting a lot richer," Oxfam notes.