It is common knowledge that the culprits of Tupac and Biggie were never apprehended. But that is no anomaly -- as it turns out, it is extremely common for rap homicides to go unsolved.

XXL conducted a study of 52 homicides in which a rapper was killed and reported that 36 of them, or 69%, remain unsolved. That makes for a clearance rate of 31%. According to a recent NPR report, the United States national clearance rate is 64.1%. Rap homicides are more than twice as likely to go unsolved as "normal" homicides.

Five rappers have already been murdered in 2015: The Jacka, Chinx, Young Ready, Glo Gang Capo, and Dex Osama. Only Capo's case has seen a suspect arrested.