I had a quick look but couldn't find one.
Looks like for federal prisons it's as high as 48.6%, but that looks like it's for all drugs not just cannabis.
It's also probably too big a leap to speculate how many people are incarcerated for drug related incidents (theft to get money to feed a habit for example). Crimes which would probably be greatly reduced in a treatment over prohibition system.
48% include drugs as a crime, but 2/3 of them have a more serious crime as well.
So I'd say the parent is right that 16% are in for drugs and would be set free if drugs were legal. The others in that 48% wouldn't be.
>So I'd say the parent is right that 16% are in for drugs and would be set free if drugs were legal. The others in that 48% wouldn't be.
Both would be set free. 16% from state prisons, 48% from federal prisons. These are two separate prison populations.