The number of violent crimes reported to police decreased 3.8 percent last year to 1.2 million, the fifth straight year of declines, the FBI announced Monday.
Meanwhile, the total number of property crimes reported to law enforcement agencies went down by 0.5 percent to 9 million, the ninth consecutive year that figure has fallen. Property crimes resulted in estimated losses of $156.6 billion.
The latest declines mark the continuation of a nearly two-decade drop in crime levels - a trend that almost no one in the field of criminology predicted, said Professor John Caulkins of Carnegie Mellon Heinz College. The trend, said Caulkins, is a reflection of a range of many factors, including policing practices.
A drop in the number of people in the peak crime-age category of teens to 25-year-olds also contributed to the crime reductions, Caulkins said, but added that "if this were only a story of demographics, we would never have had this kind of substantial decline."
Government figures released two weeks ago said that violent crime has fallen by 65 percent since 1993.
Twenty years ago, "there was a lot of hand-wringing about high crime levels" but "we're way past the possibility that this is a lucky conversion," Caulkins said.
The FBI's data showed that the South accounted for 41.3 percent of violent crime, while the West accounted for 22.9 percent. The Midwest claimed 19.5 percent of the cases and the Northeast, 16.2 percent.
Murders, rapes, robberies and aggravated assaults reported to authorities all declined last year. According to the FBI's data for last year:
-14,612 people were murdered, down 14.7 percent from 17,128 in 2007.
-83,425 people were raped, down 9.4 percent from 92,160 in 2007.
-354,396 people were robbed, down over 20 percent from 447,324 in 2007.
-751,131 people were assaulted, down 13.3 percent from 866,358 in 2007.
The FBI said firearms were used in two-thirds of the nation's murders last year, and in two out of every five robberies and in one out of five aggravated assaults.
In 2011, authorities solved nearly 64 percent of murders, over 40 percent of forcible rapes, nearly 29 percent of robberies and nearly 57 percent of aggravated assaults.
The FBI's crime reporting program, which captures crimes that are reported to police, is one of two statistical measures of crime levels issued by the Justice Department. Historically, less than half of all crimes, including violent crimes, are reported to police. The other measure, the national crime victimization survey, is designed to capture crime data whether it is reported to police or not. That survey is based on interviews of crime victims.
Two weeks ago, the victimization survey reported that violent crimes jumped 18 percent last year, the first rise in nearly 20 years, while property crimes rose for the first time in a decade. Academic experts say the survey data fall short of signaling a reversal of the long-term decline in crime.
Caulkins said that the FBI report is probably more reliable as a year-to-year measure, but that the victimization survey also is useful because it includes crimes beyond those that are officially reported.
The victimization survey found that the increase in the number of violent crimes was due largely to an upward swing in simple assaults, which rose 22 percent, from 4 million in 2010 to 5 million last year. The incidence of rape, sexual assault and robbery remained largely unchanged, as did serious violent crime involving weapons or injury.
The experts said the percentage increases in last year's survey were so large primarily because the 2011 crime totals were compared with historically low levels of crime in 2010.