Crime in Fairfax County is down more than 9 percent in 2011, after a 10 percent decline in 2010, according to police statistics that show Fairfax to be one of the safest counties in the Washington area. “We don’t know what the explanation might be,” said police spokeswoman Lucy Caldwell. “We hope it’s effective policing and excellent community participation, but it’s very hard to answer that question.”

Regardless of why Fairfax residents are behaving better than in years past, Caldwell said the declines mirror trends nationally. In 2009, homicides fell by more than 7 percent throughout the United States, according to the FBI.