With high unemployment and police departments hit by budget cuts you'd expect more crime, right?
But the FBI released statistics Monday that showed the opposite in 2010: Violent crime across the U.S. dropped 6 percent, marking the fourth straight annual decline. Property crime was down for the eighth straight year, falling 2.7 percent.
Within violent crime, robbery fell 10 percent, rape 5 percent, and murder, non-negligent manslaughter and aggravated assault more than 4 percent.
Each type of property crime also decreased. The largest, a 7.4 percent drop, was for motor vehicle thefts. Burglaries fell 2 percent and larceny-thefts 2.4 percent.
"Everyone is wondering about that," Alfred Blumstein a criminal justice professor at Carnegie Mellon University's Heinz College, says of the continued decline in crime. "Many expected the Great Recession to drive crime rates up — especially property crime rates — but so there are no good, hard explanations at hand."
There is "lots of speculations," Blumstein adds, "and we all have some, but nothing is demonstrated or proven."
Is the reason more criminals behind bars for longer periods? Not likely. "Incarceration rates have been flat and in some states have dropped in recent years, so it's unlikely that's driving the crime downturn," says Richard Rosenfeld, a past president of the American Society of Criminology and a professor at the University of Missouri-St. Louis.
So what can explain the continued decline? Several experts weighed in with these possible factors:
An aging U.S. population. "The fasted growing segment of the population are those over 50," notes James Alan Fox, a criminologist at Northeastern University. And those folks "have the lowest rate of involvement in criminal activity."
More toys, less property crime. It's possible that items once desired by thieves are now so widespread that there's less interest in them, says Greg Ridgeway, head of public safety and justice research at the RAND Corp., a nonprofit think tank. Today's cell phones and laptops were yesterday's Walkmen "and a lot of people already have them," he says.
Low inflation. Rosenfeld says he's found a tie between inflation and crime. "Crime rates tend to rise during inflationary periods and fall, or experience a slower increase, when the inflation rate drops," he says, and "inflation ran at historically low levels during the recent economic downturn — prices actually decreased in 2009 for the first time in over 50 years."
In contrast, inflation and the crime rate were both high during the recession of the 1970s and early 1980s.
"A key mechanism linking inflation to crime is the price of stolen goods," he adds. "Price increases make cheap, stolen goods more attractive and therefore strengthen incentives for those who supply the underground markets with stolen goods. The reverse occurs when inflation is low."
Moreover, "involvement in property crime is a risk factor for violence" — so that an increase in thefts can translate into more violent crimes, he says.
More and smarter policing. William Bratton, former police chief in Los Angeles and New York and now chairman of the security firm Kroll, emphasizes the shift in police funding and tactics after 1990 proved to be the most violent year on record.
"We're still reaping the benefits" of billions of federal dollars in the 1990s that went into hiring 100,000 more police, building new prisons and doing more research, he says.
That surge also saw smarter policing, he says, especially using technology to spot crimes and "get cops on the dots a lot faster."
It used to be that walkie-talkies were cutting edge technology, Bratton adds, "and now every police car has a computer."
RAND's Ridgeway agrees that smarter and better funded policing "is an important ingredient" and cites a RAND analysis of earlier studies that found that with a 10 percent increase in police in a given city, one "can expect the homicide rate to decrease on average by 10 percent."
Worries about erasing the trend
Experts acknowledge that multiple factors are at play and that there's no consensus on how significant each one is.
Rosenfeld, for example, believes that "better policing clearly plays a role in certain places, such as New York and Los Angeles, but cannot explain across-the-board crime declines because policing hasn't improved universally."
Still, experts worry crime rates might go up again after a nearly 10 percent drop per capita in police budgets in recent years.
"Lots of cuts in crime control and crime prevention," says Fox, "can create problems in the future in keeping crime rate low."
Bratton notes that "after 9/11 many of the funds for crime reduction are now focused on terrorism prevention."
Each city will have a different breaking point, he says.
New York City, for example, has 7,000 fewer police since 9/11 and "has been able to keep the city safer and safer" due to smarter policing, Bratton says.
But Bratton is also quick to note that New York had a violence uptick in 2010, with the FBI statistics showing a 14 percent increase in murders.
"We'll need to watch these next six months to see if they can push that back," he says.
And New York City wasn't alone in seeing more murders.
Boston saw a 46 percent rise, with 73 homicides in 2010. The murder rate in Newark, N.J., rose 12.5 percent.
The Associated Press and Reuters contributed to this report.