That’s not what I’m disputing, of course. I’m disputing that the grandparent’s assertion that if we (by your stats) simply lock up 1% of the population that violent crime would drop by 60%.

I mean, trivially, using our brains for a nanosecond, what if that 1% of the population is almost always 16-18 year olds when they commit those violent crimes. The 16-18 demographic is roughly 4% of the US population (Google). That would mean locking up 1 in 4 high school students for 6-20 of their most formative years, and thrusting them back into society with a “Mission Accomplished” banner hanging behind you.

Play with the numbers a bit (maybe it’s 1 in 20), but the point stands. Using imprisonment to try to quarantine a demographic that is perceived as irreparably violent is a barbaric, sophomoric idea that has very little evidence of success in the modern era.

Don't jail criminals because maybe they're young, that's your argument? Sounds like a something that's already part of the sentencing policy, leniency of first time offenders.

There are two ideas here - locking up actual criminals and locking up people who happen to fit the pattern of a criminal even without committing any crime. You're arguing against the latter, but I don't think anybody was proposing that.