Three strikes laws are a huge problem. Prisons in California are having to actually release prisoners early due to just how overcrowded they are.
Domestic violence rates being lower are probably tied into divorce, but there has been a *massive* cultural shift in how accepted it is to beat your wife. I can't overstate how much cultural mores have changed here; the violence against women act of 1994 in particular is one of the benchmarks there. Shit like martial rape was legal in some parts of the US until the 1990's. I'd bet money that the shift in culture there is more important than anything else.
That said, I was refering to the lower rate of marriage and the out of wedlock rate in particular.
http://www.economist.com/news/united-states/21569433-americas-marriage-rate-falling-and-its-out-wedlock-birth-rate-soaring-fraying This is not an academic source, but it does cover some the statistics about the marriage rate. In particular, marriage is becoming something reserved for middle and upper class whites. This is more than a cultural shift away from shotgun weddings, it is entire groups of not getting married. I can dig up some academic sources if you want, that just works for a casual look see.
Studies done have found a strong statistical correlation between higher punishment and lower crime.
I'm going to need a source on that. Yes, the neoclassical model of punishment does argue that, but every policy I've seen pursued in the west argues otherwise.
But if you made the death penalty the default sentence for oh, say, insider trading? Almost certainly there would be far fewer cases of insider trading in the US.
Um, no. Insider trading and white collar crime is *extremely* difficult to catch. That's the rub. You can make a penalty as harsh as you like, but it won't do any good if you can't actually catch people. Keep in mind that people who do insider trading also have th emoney to afford good attorneys. You don't think they would spend their fortunes to avoid death, or even use violent methods to deter whistleblowers and cover up wrongdoing?