Most parts of metro Atlanta saw a decrease in crime last year, mirroring a national trend that has experts baffled.

Violent and property crimes across the nation declined for the fifth straight year, by 3.8 percent and 0.5 percent respectively, when compared to 2010 estimates, according to the FBI’s Uniform Crime Report for 2011 released on Tuesday. The exceptions to the trend in metro Atlanta included the unincorporated portions of Fulton and Clayton counties.

And while the Atlanta Police Department posted a slight increase in violent crimes from 2010 to 2011, the totals are far lower than they were in 2001 for that category and property crimes. Atlantans have not seen crime figures drop this low since the 1960s, said Robert Friedmann, professor of criminal justice at Georgia State University.

In fact, just in the past decade, the Atlanta Police Department’s violent crimes have been slashed nearly in half, while its property crimes were cut by nearly a third.

The statistics continue to surprise criminologists. Historically, high unemployment rates have tended to coincide with high crime rates.

“For years, that has been the association, and this is the exception,” Friedmann said. “There is a major economic downturn, and it is not yet accompanied with an uptick in crime statistics.”

Greg Scott, vice president of public safety for the Inman Park neighborhood association in Atlanta, has written a column about crime for the neighborhood newsletter since 2007. He said some neighbors — especially newer ones — may have the perception that crime has increased because of a few high-profile incidents in recent months, such as the armed robbery of the North Highland Tavern in June and a police shooting of a car thief in September.

However, Scott said robberies are few and far between, and property crimes such as car break-ins and burglaries are now occurring far less often than they used to five years ago.

“The folks that are engaged and go to the meetings and hear the police reports understand there’s been a shift and that crime is actually down,” Scott said. “The folks that aren’t engaged are the ones I’ve gotten communications from. They are a little bit alarmed because of the high-profile crimes.”

Fulton and Clayton county police departments were the only jurisdictions that tallied significantly more incidents of violent and property crime in 2011 than the prior year. Those two counties also have been hard-hit during the recession with job losses and the housing slump.

An increase in robberies and aggravated assaults over the prior year drove Fulton County Police Department’s violent crime totals up 12 percent in 2011. Slight increases in property theft and motor vehicle theft also nudged the department’s 2011 property crime totals 5 percent higher. The Fulton statistics represent the unincorporated portions of the county, and don’t include crimes that happened in the cities of Sandy Springs, Alpharetta, Johns Creek and Milton, which report separately because they have their own police departments.

The Clayton County Police Department saw a surge in burglaries, larcenies and motor vehicle thefts that lifted property crimes 8 percent. The department’s violent crime total in 2011 was nearly the same as it was the prior year; however, murder and manslaughter cases more than doubled from 12 to 28.

Clayton County District Attorney Tracy Graham Lawson said that’s still a substantial improvement over the number of homicide cases the department regularly handled five years ago. In 2007, FBI records show Clayton County police responded to 35 murders and manslaughters.

Lawson could think of no reason why slayings went up again last year following such dramatic declines.

“It may just be kind of a fluke,” Lawson said. “We’ve had a fair number of drug murders, but I’m actually a little surprised they were up as much as they are.”

It’s difficult to know if the downward crime trend most of the metro area is seeing will continue or if it has bottomed out. Friedmann said he has noticed a slight uptick in crime so far this year.

“It will be interesting to see what 2012 will bring,” Friedmann said.