I was recently asked whether I had any data to support the claim that the number of mentions of the LAPD (Los Angeles Police Department) in hip hop lyrics has fallen off in recent years, after peaking in the mid-1990s. The LAPD attracted a lot of angry attention from hip hop artists in the wake of the 1992 LA riots, triggered when four LAPD officers were acquitted of using excessive force in the arrest and beating of Rodney King. 

On the face of it, this claim should be easy to check: use a lyrics database to search for hip hop songs mentioning “LAPD”, find when they were released, and look at the trend. In practice, it turns out to be rather more complicated.