always been curious about this--how does billboard, or any chart for that matter, determine how an artist lands on multiple charts? i mean take, Prince for instance. 3121 debuted at #1 on the hot 200 and the r&b charts. most places that sell music today (FYE, Best Buy, Circuit City, Walmart, Target etc) usually have pop/urban music lumped together--so how would an album like 3121 remain high in one chart and freefall on another? is there some code that retailers use to determine this?