Ideally, any effective genre chart—be it R&B, Latin, country, even alt-rock—doesn’t just track a particular strain of music, which can be marked by ever-changing boundaries and ultimately impossible to define. It’s meant to track an audience. This is a subtle but vital difference. If an R&B chart tries to cover whatever might be termed R&B music, you get into the subjective, slippery business of determining what, or who, is “black enough” for the chart. That wouldn’t be appropriate for Billboard, a purportedly objective arbiter of the music business.
The goal is not to racially profile record buyers, either. Instead, by tracking the R&B and hip-hop audience—those who seek out black radio stations and maintain a steady diet of beats, rhymes, and soul, regardless of their own ethnic makeup—you get a much better read of the pulse of actual fans of the music: those who live and breathe it, week in, week out. That used to be what Billboard’s R&B/Hip-Hop Songs chart did. It’s not what it does anymore.
– Chris Molanphy, in Pitchfork, does what he does, and then some, with a fascinating delve into the changing nature of the r&b charts