WASHINGTON — The Federal Bureau of Investigation said Tuesday that violent crimes, including murders, fell by 5.4 percent in the first six months of 2013 compared with the same period in 2012, continuing a long reduction in violent crime across the country.

The only category where the number increased was rape, but that number is slightly misleading because the 2013 figure is based on a broader definition of the crime adopted by the Justice Department. In 2013, 14,400 rapes were reported, compared with 13,242 in 2012.

Property crimes also fell significantly, and of all the crimes the F.B.I. tracks — both violent offenses and nonviolent ones — the greatest drop-off, by percentage, was in arsons, which fell by 15.6 percent.

“We have had almost 25 years of a decline in crime, but on a year-to-year basis it’s hard to come up with a story,” John Roman, a senior fellow at the Urban Institute’s Justice Policy Center, said, referring to efforts to pinpoint reasons for the lower numbers. “But over all, this shows how we’ve gotten smarter on policing, immigration and gentrification in the cities and elsewhere.”