There is no such thing as a root cause. The economy is a dynamic system under a legal framework which governs the way it works. A lot of that legal framework is designed to punish the poor and punish minorities which makes them poor. It's doubly troubling and to tackle inequality requires tackling the legal and social framework our economy exists in which happens to have institutional racism and sexism.

In other words, does racism and gender create the income inequality we see across the board? No, but is getting rid of racism and gender inequality required to diminish income inequality? Yes.