In six states, plus the District of Columbia, blacks are over five times as likely to be arrested for marijuana possession than whites are. The national average? Black Americans are arrested nearly four times as much. And it's not because of increased use of the drug: according to the New York Times's report, black and white Americans have about the same rates of marijuana use overall. So what's going on?

Essentially, the Times explains, it's probably one of a handful of biases written into the system of local law enforcement nationwide. The data they're using is from 2010, and was also used by the ACLU for a new report. The ACLU cites the Edward Byrne Justice Assistance Grant Program as one possible reason for the disparity. That's because, they explain, the program incentivizes increasing drug arrest numbers by tying the statistics to funding. Law enforcement officials then concentrate on lower income neighborhoods to keep those numbers up, finding the lowest hanging fruit of crimes to enforce. 

The argument resonantes with criticism of the NYPD's "stop and frisk" program, which overwhelmingly targets young, black or latino men in the city (and, indeed, demonstrates a racial disparity in arrests for marijuana possession). But as the ACLU and the Times show, the problem of racial bias in arrests for possessing a drug that is, after all,  gaining acceptance across the U.S., is a national one. the ACLU found a bias in "virtually every county in the country," they told the Times, regardless of the proportional population of minorities in that county. 

Source: ACLU

The disparity is worst in the Northeast and the Midwest, as the Times's map shows. Currently, marijuana possession is legal in Colorado and Washington state. Eighteen states have laws regulating medicinal use of the substance.