Unemployment is high, the economy is down. Yet for all the signs of recession, something is missing: More crime.

Experts are scratching their heads over why crime has ebbed during this recession, making it different from other economic downturns of the past half-century. Early guesses include jobless folks at home keeping closer watch for thieves, or extra benefits keeping people from resorting to crime.

Preliminary figures gathered by the FBI for the first six months of 2009 show crime falling across the country — at a time when many experts and police officials had expected crime to rise under the pressure of high unemployment, foreclosures and layoffs.

Murder and manslaughter dropped a surprising 10 percent for the first half of the year, according to the FBI's data.

"That's a remarkable decline, given the economic conditions," said Richard Rosenfeld, a sociologist at the University of Missouri-St. Louis who has studied crime trends.

Rosenfeld said he did not expect the 10 percent drop in killings to be sustained over the entire year, as more data is reported. But he said the broad declines are exceptional, given that past recessions have boosted crime rates dating back to the 1950's.

The professor said there are several possible explanations, including that extended unemployment benefits and other government attempts at economic stimulus "have cushioned and delayed for many people the big blows that come from a recession."

Those benefits will have to run out eventually, he cautioned.

Another possible factor is that with more people home from work, it is harder for burglars to break into a home or apartment unnoticed by neighbors, he said. Rosenfeld said another possibility is that because big cities tend to have an outsize impact on crime statistics, those cities' so-called "smart policing" efforts are still working to drive down rates.

"What you see are the large cities, Chicago, Los Angeles, New York in particular are down considerably, and those large cities are driving the overall change," he said.

Overall, violent crimes fell by 4.4 percent and property crimes dropped by 6.1 percent, according to the data collected by the FBI. Crime rates haven't been this low since the 1960's, and are nowhere near the peak reached in the early 1990's.

The new figures show car thefts also dropped significantly, falling nearly 19 percent and continuing a sharp downward trend in that category. Some believe that big drop in car theft is due largely to the security locking systems installed on most models, as well as more high-tech deterrents like global positioning systems.

The figures are based on data supplied to the FBI by more than 11,700 police and law enforcement agencies. They compare reported crimes in the first six months of this year to the first six months of last year.

The early 2009 data suggests the crime-dropping trend of 2008 is not just continuing but accelerating. In 2008, the same data showed a nearly 4 percent drop in murder and manslaughter, and an overall drop in violent crime of 1.9 percent from 2007 to 2008.

According to the FBI figures, reports of violent crime fell about 7 percent in cities with 1 million or more people. But in towns with 10,000 to 25,000 people, violent crime ticked up slightly by 1.7 percent.

Each city's data was different, but collectively pointed to less crime in every major category.

Nationwide, rape fell by 3.3 percent, and robbery by 6.5 percent. Arsons, which are subject to a variety of reporting standards, declined more than 8 percent.

The FBI's data for New York City shows 204 reported murders in the first half of 2009, compared to 252 in same period last year. By comparison, Oklahoma City saw reported killings increase from 26 to 32, the FBI said. Phoenix, Ariz., saw 10 fewer killings, dropping from 86 in the first half of 2008 to 76 in the first half of this year, according to the data.

Separate statistics compiled by the Justice Department measure both reported and unreported crimes.