I don't have any data on WA's black market vs white market, but I do have some anecdata: the thriving community of illicit entrepreneurs hanging out by the U Di

I don't have any data on WA's black market vs white market, but I do have some anecdata: the thriving community of illicit entrepreneurs hanging out by the U District Jack in the Box has completely vanished since legalization. (And it is quite literally a black/white thing, too - the people selling weed in shops are pretty much uniformly white, whereas the illegal market was a lot more mixed-race.)