(The drug use infused lies continue – Let’s not let facts get in the way of a good marijuana myth!)
We also don’t have good data for state prisons — where more than 87 percent of US prison inmates are held, based on federal data. But we do know that a minority of state prisoners are in for drugs: In 2015, 3.4 percent of all state prisoners were in for drug possession and 11.7 percent were in for other drug-related crimes. So, again, only a fraction of prisoners are locked up due to drug prohibition in general, much less marijuana prohibition in particular.
We do have some good data for the federal system. According to the US Sentencing Commission, 92 of nearly 20,000 people — fewer than half a percent — sentenced for drug offenses during fiscal year 2017 were locked up due to simple possession of marijuana. And drug cases made up less than a third of cases reported by the Sentencing Commission that year. Not all of these people were sentenced to prison; some got probation instead.
Based on the data we do have, though, it’s fair to say that marijuana prohibition — and even the war on drugs more broadly — is not the major driver of mass incarceration.