The Atlantic on that great violent crime drop that occurred in the US in the 1990's:
By decade’s end, the homicide rate plunged 42 percent nationwide. Violent crime decreased by one-third. What turned into a precipitous decline started later in some areas and took longer in others. But it happened everywhere: in each region of the country, in cities large and small, in rural and urban areas alike. In the Northeast, which reaped the largest benefits, the homicide rate was halved. Murders plummeted by 75 percent in New York City alone.
But the forces that drove the Great American Crime Decline remain a mystery. Theories abound among sociologists, economists, and political scientists about the causes, with some hypotheses stronger than others. But there’s no real consensus among scholars about what caused one of the largest social shifts in modern American history.
The author explores a few of the claimed reasons for the massive trend change citing a range of studies.
It is fascinating that we still don't have a better idea. It would be such a valuable and beneficial thing to know so that violent crime could be reduced elsewhere. The policies could be further refined and improved. The dramatic drop in violent crime numbers was impressive.
I've got my own ideas of what the major causes were looking at the various claims. However I think a lot of the apparent success was due to the very high numbers of the 90's in general. The situation was pretty horrible. Almost any measure would have had some effect.
I think most people have their opinions on this.