Whenever we talk about gentrification, it really is a good idea not simply to understand who's coming and who's going but precisely when the coming and going happened. In reference to our conversations around Washington, D.C., it's really important to understand that the black population was falling in the city long before the advent of hipsters, interlopers and white people in general.
Washington's black population peaked in 1970 at just over half a million (537,712, to be precise). It's declined steadily ever since, with the biggest decline occurring between 1970 and 1980, when almost 100,000 black people left the city. Whites were also leaving the city by then, but at a much slower rate — the major white out-migration happened in the '50s and the '60s.
Read Ta-Nehisi Coates' entire blog post at the Atlantic.