Just a sanity check: "Researchers have studied the decline in firearm crime and violent crime for many years, and though there are theories to explain the decline, there is no consensus among those who study the issue as to why it happened."
If I had to guess, I'd say it's because it's harder to get away with a gun crime now than it used to be. TV shows like CSI probably have more to do with the decline in gun violence than any other environmental factors.
