This is from the FBI Uniform Crime Statistics. You can see that there is a fairly low rate of violence in the '50s and the '60s, then it soared upward for several decades, and began a precipitous decline, starting in the 1990s, so that it went back to the level that was last enjoyed in 1960.
これは FBI がまとめた他殺の統計です 50年代と60年代は暴力が抑えられていましたが その後 何十年か高めの数字を経て 1990年代に激減し始め ほぼ60年代のレベルへと戻りました