My 9 year old daughter is debt free, but doesn't really have any income. That places her as wealthier than 2 BILLION people (with negative net worth) using your methodology!
There are "lies, damn lies, and statistics." Your use of statistics falls into that category.
It doesn't matter how wealthy people are compared to each other, unless your overwhelming consideration is jealousy. It matters how wealthy people are compared to how wealthy they used to be.
Also "the bottom 90 percent became poorer" is an inaccurate statement, unsupported by the data. If you took the people considered part of the "bottom 90 percent" in 2009 after the housing/financial crisis, those specific people have as a whole become wealthier. The current group of people (in 2014) they might rate as the "bottom 90 percent" are a significantly different set of individuals, many of whom were not in the "bottom 90 percent" in 2009.