Poverty cannot be the primary reason, says Jack Levin, a criminologist at Northeastern University in Boston.

ECONOMIST: Oakland

Jack Levin, a criminology professor at Northeastern University in Boston, acknowledges the success of policing strategies, but notes that an ageing society like the United States should expect to experience less violent crime.

ECONOMIST: The great crime decline continues. No one is sure why

But background checks would not have stopped most school shootings, in which the gunmen took legally obtained weapons from parents with spotless backgrounds, says Jack Levin, a professor of sociology and criminology at Northeastern University in Boston.

BBC: US gun debate: Could Obama's guns plan work?