Violent crime has plummeted in the Washington, D.C., area and in other major cities, a trend the Washington Post says criminologists describe as baffling and unexpected. Washington, New York, and Los Angeles are on track for fewer killings this year than in any other year in at least four decades. Boston, San Francisco, Minneapolis and other cities are also seeing notable reductions in homicides. Detoit is up, however. “Experts did not see this coming at all,” said Andrew Karmen, a criminologist at John Jay College of Criminal Justice. Criminologists have different theories about why crime is down so much, although many agree that the common belief that crime is connected to the economy is false. Whatever the cause, police often take credit for the drop. “Everybody wants to beat us up when it goes up, so we’ll take credit for it when it goes down,” Washington Police Chief Cathy Lanier said.