http://www.newyorker.com/arts/critics/atlarge/2009/11/09/091...
Philadelphia is one of many city's in the US, but looking at the overall trend and including things like duels shows a different picture. Consider, some gang violence would not have counted as murder 100 years ago.
It's also undeniable that until the Victorian period, Europe was generally becoming more orderly. (You'd probably see a drop in testosterone levels if you could measure this.) The trouble is that we live on the other side of that curve. See under: http://en.wikipedia.org/wiki/Sensitive_urban_zone. ("ZUS" is French for "no-go zone.") But fudge and blur enough and you can hide the peak.
I'd love to see Professor Spierenburg take a walk in Les Musiciens someday. His name sounds Jewish. Perhaps he'd be kidnapped, tortured and burned alive, like Ilan Halimi. But before he died, would he change his mind? Statistics suggest the contrary.
And what about Union busting. 50 people died from http://en.wikipedia.org/wiki/Paint_Creek-Cabin_Creek_strike_... can you imagine what would happen today if the same level of violence became national news? Yet, for the time while it was larger average such things where not all that uncommon.
Looking at http://www.deathpenaltyinfo.org/murder-rates-nationally-and-... you can see a 11x difference in 2010 murders between Louisiana 11.2 and New Hampshire 1.0. But, considering the amount of migration within the country I think a national perspective is necessarily. And nationally, 200 years ago things where a lot more violent.
PS: Granted, it's not hard to twist these statistics if you include vehicle accidents the numbers start to change dramatically.
In 1894 Philadelphia, a city of a million people at the time (2/3rds the current population) recorded 22 murders. By 1990 the murder count peaked at 535 before falling a bit back to around ~300 the past few years. Overall that's a 1000%+ increase between 1894 and now. So even by historical American standards, crime now is much worse. Part of the change in Philadelphia is due to the great migration and the changing composition of the population rather than change in law enforcement. But even adjusting for demographics the crime rate is 2-4X that of the 1890's http://books.google.com/books?id=8CVNAAAAMAAJ&pg=PA13...
I'm still trying to figure out what precisely changed about law enforcement between the 1890's and the 1980's. Many books mention in passing that the Warren court and more liberal policing policy in the 1960's played a role (the books "Slaughter of the Cities" and "Unheavenly City" mention this a bit, among others). But I still haven't found a good treatment that details how these policies made their way from the courts and the mayors to the beat cops on the ground, and how the day to day job of policing and sentencing actually changed.
BTW, mencius, do you ever worry that policing in Europe or Japan is too stringent? That it will lead over time to a domestication of the population, a winnowing out of the masculine and risk taking character in the population?
-devin f