[wtmcc]

Probably the best citation is a remarkable, rigorous paper by Chetty et al (2014) that uses individual IRS returns [1].

To quote those authors: “We find that children entering the labor market today have the same chances of moving up in the income distribution (relative to their parents) as children born in the 1970s. However, because inequality has risen, the consequences of the ‘birth lottery’ – the parents to whom a child is born – are larger today than in the past.”

[1] http://obs.rc.fas.harvard.edu/chetty/mobility_trends.pdf