The shift from brick-and-mortar CD stores, the ones that made gangsta rap a major commercial force in the dawn of the SoundScan era two decades ago, to digital sales has had a lot of indirect effects on the music industry. One of those is that certain listeners are more likely than others to get their music on the iTunes store. And whether it's simply those demographic differences, or the fact that they haven't given away most of their music on free mixtapes, there's been a definite shift towards not just the always popular Eminem but also Mac Miller and Macklemore & Ryan Lewis (to say nothing of the white R&B singers who've run the charts this year, Justin Timberlake and Robin Thicke). After all the hoopla about French Montana returning Bad Boy to rap glory, Machine Gun Kelly ended up with the label's best-selling hip-hop release of the last couple years.
White rappers totally run iTunes.