While, on paper, increasing the prison sentences sounds like it will reduce crime rates (I held that belief myself at one time), mountains of statistical evidence would show us otherwise...which is what ended up changing my mind on the subject.
The link between crime and poverty is an unmistakable one.
I'll preface my next statement with the following stat:
88% of people will end up in the same economic situation as their parents (statistically speaking)
So, if you're a young person living in the inner city, here are essentially your options.
1.) Work hard/study hard and gamble on the odds that you'll be one of the 12% that makes it out.
2.) Give up and resign to the fact that you're going to be poor.
3.) Find a way to get money through less-than-legal means.
Locking people up for longer doesn't address the underlying causes for for why they're choosing option 3 in the first place (Legitimate opportunities are limited; but they don't want to be broke)
The answer is giving them a 4th option. The countries that have given a 4th option (Free college education) have realized 40%+ reductions in their crime rates within 10 years as a result. ...and it's been done in enough countries that we can't say it's a fluke...as to where our system of over-penalizing hasn't dropped our crime rates one bit.
Free education is the one place where I stray from the libertarian platform...because, to me, if Rich Johnny with a 2.5 GPA gets to go to college because of his parents' high income debt fre, but Poor Billy with a 2.5 GPA cannot because of his parents' low income (unless he wants 10 years worth of student loans to pay back), one can't really say that Johnny and Billy had an equal chance to succeed and prosper in life.
***I made sure to mention the 2.5 GPA and the loans aspect since the typical rebuttal to this is "Well, he could've just worked hard and gotten a scholarship", or "He could've just taken on student loans" I wanted to make it apparent that we should be discussing the average scenario, and not the rare cases where a kid has such an exceptional level of intelligence that schools are knocking down there door to get them to go there for free.