A shopping mall in downtown Flint, Mich.: Flint has the highest rate of violent crime of any U.S city with more than 100,000 people, but violent crime across the country has dropped 4 percent since 2010 and 38 percent since the peak in 1992.

Bob Krist/CORBIS

he conventional wisdom is that crime rises during hard economic times. Well, either that's wrong or the economy isn't really that bad, according to new preliminary national crime statistics from the Federal Bureau of Investigation. In fact, U.S. crime rates in 2011 hit their lowest levels since World War II, University of Maryland criminologist Gary LaFree tells MSNBC. Experts cite a number of possible reasons for the prolonged drop in crime, including better policing techniques, an aging population, and, somewhat counterintuitively, the unifying effects of the recession. Here's a look at our Leave It to Beaver–level crime rates, by the numbers:

4
Percent drop in violent crime (including murder, rape, and robbery) from 2010 to 2011

5
Consecutive years violent crime has fallen

38
Percent drop in violent crime from the peak in 1992

0.8
Percent drop in property crime (including burglary, larceny, and auto theft) from 2010 to 2011

9
Consecutive years property crime has fallen

30.6
Percent drop in property crime since the peak in 1991

5
Percent drop in arson from 2010 to 2011

4
Percent drop in forcible rape

4
Percent drop in robberies

3.3
Percent drop in car theft

1.9
Percent drop in murder

14,468
Total approximate murders in the U.S. in 2011

280
Decrease in murders from 2010 to 2011

1968
Last year the total number of murders was lower, at 13,800

18.3
Percent increase in murders in cities with populations under 10,000

14.4
Percent decrease in murder in cities with populations of 50,000 to 99,999

51,209
Violent crimes in New York City (pop. 8.2 million), including 515 murders — the highest total of any U.S. city

2,392
Violent crimes in Flint, Mich. (pop. 102,357), including 52 murders — the highest rate of any city of 100,000+

95
Violent crimes in Temecula, Calif. (pop. 101,274), including 0 murders — the lowest total of any city of 100,000+ 

120
Violent crimes in Irvine, Calif. (pop. 214,872), including 2 murders — the lowest rate of any city of 100,000+

14,009
Law enforcement agencies the FBI gathered its numbers from

37.2
The median age in America, a historic high. "There is some truth to the fact that younger people commit more crimes," LaFree tells MSNBC.

Sources: Discovery News, FBI (2,3), Huffington Post, Los Angeles Times, MSNBC, Reuters, 24/7 Wall St.