The problem here is knowing what really is the cause and what is the effect. It is well known that, in the United States, drug usage between all races tends to

The problem here is knowing what really is the cause and what is the effect. It is well known that, in the United States, drug usage between all races tends to trend roughly the same. However, the arrest rate for blacks is much, much higher. See these charts for marijuana. https://www.washingtonpost.com/news/wonk/wp/2013/06/04/the-blackwhite-marijuana-arrest-gap-in-nine-charts/ https://www.washingtonpost.com/news/wonk/wp/2013/06/04/the-b... One possible explanation, of course, is indeed that blacks are more likely to be arrested while committing another serious crime. Hence the gap. An alternate explanation reverses the argument: blacks may be more prone to commit serious crimes because they are more likely to be arrested for trivial crimes like marijuana usage. Prison does have social consequences after all (eg, people are less willing to hire someone with an arrest record; prison can establish contacts with underground economies that are more likely to utilize violence to settle disputes; prison can tear apart families; etc. -- http://www.economist.com/node/708550 http://www.economist.com/node/708550 ) and since America is not keen on reintegrating criminals into society (a very high rate of recidivism compared to most countries -- http://www.salve.edu/sites/default/files/filesfield/documents/Incarceration_and_Recidivism.pdf http://www.salve.edu/sites/default/files/filesfield/document... and http://www.businessinsider.com/why-norways-prison-system-is-so-successful-2014-12 http://www.businessinsider.com/why-norways-prison-system-is-... ), it is very possible that early arrests for modest crimes lead to later arrests for worse crimes later.