Facts
The largest number I've ever seen from any even marginally-documented source--and even that was still fuzzy--was 1 percent owning something like 35 percent of the wealth.
There is no viable source for a 90 percent figure, and I don't care who the hell tries to tell me otherwise. This isn't arrogance. It's facts. I still suspect you heard that number from either the interviewer, who I suspect was a NPR type, or inside your own head. Give me a source.
Of course, the only reason for pushing these numbers in the first place is to justify taking it from them.