Crime was down in six of 10 categories in Haverhill last year, according to Police Department statistics, with burglary showing the biggest decrease in incidents.
According to the Police Department's crime analysis unit, the number of burglaries dropped from 803 in 2010 to 484 last year, a decline of 40 percent.
The FBI defines burglary as the unlawful entry of a home or other structure to commit a felony or theft.
Despite the apparent good news, however, Police Chief Alan R. DeNaro declined to answer questions about the reasons for the sharp decline in burglaries.
Other crimes that were down in 2011, according to the official statistics, were homicide, forcible rape, vandalism, narcotics and prostitution.
Percentage-wise, prostitution showed the biggest decrease. The number of incidents dropped by 74 percent, from 34 in 2010 to nine in 2011.
Over the past two years, the Haverhill Police Department has aggressively pursued prostitution as a "quality of life" crime, staging undercover stings to catch street-corner prostitutes and their customers. Police have also cracked down on massage parlors offering illicit services.
The four categories of crime that showed an increase were motor vehicle theft, larceny, robbery and assault.
Motor vehicle thefts showed the sharpest increase, up from 124 in 2010 to 150 in 2011, an increase of 21 percent.
Larcenies were up 4 percent, rising from 956 to 995. The FBI defines larceny as the unlawful taking of another's property. The category includes shoplifting, bike thefts and other acts of stealing that do not involve force. Robbery is theft by force or threat of force.
Despite progress fighting crime, Deputy Chief Donald Thompson said the department will continue exploring ways to reduce property crime and crimes of violence.
Thompson said neighborhoods where residents actively keep an eye on suspicious activity provide the best defense against crime.
His advice to residents: "Keep an eye on your property and an eye on your neighbor's property."
Mayor James Fiorentini noted the decrease with pride in his recent email newsletter.
"We do not really know what causes crime numbers to go up and down, but we do know this: we have an excellent police department and we are proud of them," he said.
Haverhill crime, 2010 vs. 2011
Crime20102011number changepercent change
Motor vehicle theft1241502621
Source: Haverhill Police Department