Some criminal law experts said the kind of discrepancy seen in Camden has been the result of deliberate downgrading of crimes by image-conscious police departments in other cities. Camden authorities have declined to release documents - incident reports - that could hold the answer.
Simple assault, which can include intimidation and fights that do not cause serious injuries, falls outside the "violent crime" category defined by the FBI.
Criminal justice experts say such crimes are an important law enforcement gauge: Left unchecked, simple assaults can lead to more serious crimes, much as one abandoned house can bring down a whole block.
Scott Thomson, chief of the Camden County Police, whose Metro Division replaced the city police department a year ago, suggested that one reason for the higher simple-assault numbers could be that more residents are reporting such assaults to officers, whose numbers have grown.
Thomson, however, could not explain why the increased interaction with officers did not similarly result in higher numbers of other crimes, such as aggravated assault and robbery.
Later, in an e-mail Friday, he also said the department had begun to include social-media and text-message threats in simple-assault data.
"Perhaps other police departments are either not aware or have not yet adopted the State Police recommended practice of categorizing electronic or social media threats from [an] October 2013 training course," he wrote.
He added that the department statistician has more than 16 years of experience and that the numbers receive a clean bill of health each year from a State Police audit.
Some experts say another explanation might be that assaults are not being recorded in the appropriate categories.
"It's not so hard to classify an incident as a simple assault, frankly," said Robert Apel, an associate professor at Rutgers University's School of Criminal Justice, who spoke in general terms and not particularly about Camden. "There's an awful lot of discretion left to the officer to make that determination."
That decision carries weight in court: Simple assault is often a misdemeanor and carries a small fine. Aggravated assault is generally a felony and can lead to prison time.
In the late 1990s, Philadelphia police came under fire for downgrading many aggravated assaults to simple assaults in an attempt to improve the department's image. In 2009, Dallas police were criticized for doing the same thing.
Apel and others say that more data are needed to confirm a trend and that assault numbers can fluctuate. But it raises questions, they say, when the numbers of aggravated- and simple-assault victims move as far in opposite directions as they have in Camden.
"The question is, Is it real, or a downgrading effect?" said Thomas Arvanites, director of Villanova University's criminology program. "And I don't know how you would explain it being real."
The FBI, in compiling its annual Uniform Crime Report, defines simple assault as a verbal threat or, more often, an attack that does not involve a weapon or serious injuries such as broken bones, knocked-out teeth, or stitches. If such injuries or a weapon are involved, the FBI says, the crime should be reported as an aggravated assault - making it a violent crime.
But the FBI acknowledges that "aggravated assault is a troublesome crime to classify."
An accurate study of how crimes are recorded would require access to police incident reports. Camden police and the county have repeatedly denied The Inquirer access to the reports, saying they are confidential investigatory records.
A 'model' for others
That differs from police practice in cities such as Boston and Washington, which do release the reports. In Philadelphia, according to a department spokeswoman, the narrative in the reports is sometimes read back to reporters.
On Tuesday, Christie came to Camden and lauded the drops in aggravated assault and other crime categories.
(In August, reporting on the first three months after the new force began patrolling Camden, authorities similarly noted declines in several violent crimes.)
Last week, the governor called the county police department, which was created in April 2013 after the controversial disbanding of the city police department, a "model" for other cities to emulate.
According to data released by police in April, homicides in the city dropped from 13 to 10, and there was a 28 percent drop in aggravated-assault victims - from 227 to 163 - in the first quarter compared with the same quarter a year ago.
But when simple assaults are included, assaults in the city rose 12 percent.
In April, according to Camden police, the number of simple-assault victims was 195. This was considerably higher than in any of the first four months of last year, when, according to State Police data, the highest number was 146.
Freeholder Director Louis Cappelli Jr., described on the Camden County website as the "architect" of the county police department, said Thursday that the focus on simple assaults "amazes" him when other crimes are down.
"All numbers are concerns," said Mayor Dana Redd, but she said residents were typically more concerned with major crimes, such as homicide, robbery, and aggravated assault.
Laura Sánchez, a social worker who has lived in Camden's Fairview neighborhood for 14 years, said she was disappointed police and city officials had not talked about the spike in simple assaults.
"It concerns me that we haven't heard about it, because I would want full disclosure on their part. If we are to trust completely the change to Metro, then we have to have all the information, not just the good news."