In his Dec. 20 inaugural address, Pittsburgh Mayor Luke Ravenstahl said 2007 has been "the safest year for our citizens in more than 40 years."

That raised a few eyebrows among some officers in the Police Bureau and in neighborhoods beset by shootings.

The mayor drew his conclusion from aggregate figures for all serious crimes through November provided by the police chief's office.

The raw numbers for Part 1 crimes -- homicide, robbery, rape, arson, aggravated assault, theft, motor vehicle theft and burglary -- do indeed show them at an all-time low.

As of Nov. 30, the city recorded a total of 15,966.

December's figures haven't been collected yet, but last week it appeared that 2007's tally will come in under the previous record low of 18,702 set last year.

"Crime is decreasing," said Assistant Police Chief Paul Donaldson. "We are on track to have the lowest totals in 40 years. We've made significant strides."

But, as is often the case with crime statistics, the numbers can be deceiving.

For one thing, the city is half the size it used to be, but an analysis of crime trends over time shows that some offenses have not dropped by the same proportion as the population has declined through the decades.

In addition, some violent crimes -- particularly aggravated assault -- are actually up this year.

So is Pittsburgh really the safest it's been since 1967?

"For most people, safety relates to violence, and adding all the crimes together conveys a very different sense [than reality]," said Alfred Blumstein, a criminologist at Carnegie Mellon University. "We are most concerned about assault, homicide, rape and robbery. They really should be treated separately [from property crimes]."

It's true that the Pittsburgh area continues to enjoy one of the lowest crime rates in the nation, according to the FBI's Uniform Crime Reports.

What's more, the region fares much better in per capita crime -- offenses per 100,000 -- than similarly-sized areas such as Milwaukee, Cincinnati and Memphis.

Any trends also have to be considered in the context of historic lows nationwide, at least until the recent upticks in violent crime in 2005 and 2006.

Still, lumping all Part 1 crimes together as a measure of security for the citizenry ignores the fact that spikes in some offenses, such as shootings, are offset by decreases in others, like burglary or auto theft.

As of Nov. 30, the city had seen increases in aggravated assault, rape and arson compared to the same time last year. There are relatively few rapes and arsons every year, so calculating a percentage increase for such small numbers can be misleading.

But aggravated assaults are up about 5 percent, from 1,513 by this time last year to 1,603 this year. This year's figure for that crime is also already above the 10-year average of 1,548 aggravated assaults per year between 1995 and 2006.

Homicides were also slightly up this year, although those figures are skewed by how they're calculated.

Unofficially, there were 63 killings as of Friday, but that number includes five young children who died in a Larimer fire in June when their mothers went to a bar and left them in the care of two 8-year-olds. The boys ended up playing with matches in the middle of the night and setting the house ablaze.

The medical examiner's office categorizes those deaths as accidental.

The year's murder total also includes two police shootings, which are not reported to the FBI.

Regardless of the exact number, the city usually records roughly 60 murders every year and did again in 2007. But if Pittsburgh is the safest it's been since the late 1960s, that number should be dropping along with the population -- and it isn't.

In 1970, for example, there were also 63 murders. But the population was 520,000, about 200,000 more than it is today, so the murder rate is substantially higher now than it was then.

So is the assault rate. There were 1,646 assaults in 1970, not far from this year's total despite the much smaller population.

Of course, lots of factors can skew historical data, including different reporting standards for various crimes and, in the case of shootings, improved medical care that saves lives.

Many of today's aggravated assault victims, for example, would have been yesterday's homicides if not for developments in emergency medicine.

Statistics aside, police acknowledge that crime remains a big problem in the city, particularly gun violence among young black men.

But police say they're better equipped to handle crimes of all kinds than in years past because of improved technology, like computers in squad cars, and such initiatives as task forces of federal agents and local officers.

"It's smarter policing," said Chief Donaldson. "We are seeing results."

Overall, the year proved fairly typical, not only in Pittsburgh but for all of Allegheny County. Usually about 100 people are murdered here each year, and that proved to be the case again.

The county homicide unit was a little busier than usual, handling 42 slayings, including that of Paula Lanz, whose body was discovered in a burning van in Nashville, Tenn., in February, and Melissa Galiyas, whose bones were found last week by a hunter in Clairton.