But inherent flaws in data make those statistics unreliable and possibly misleading because thousands of crimes every year go unreported by police departments.
The drop in crime probably was closer to 2 percent, according to an analysis by The Morning Call that compared only departments that reported numbers in both years.
Data problems make it nearly impossible for anyone to home in on trends occurring in geographic regions smaller than the state as a whole. And larger departments that do not report disqualify themselves from state grants to be used for fighting crime.
''The voluntary numbers really are meaningless if you want to look at the true nature of crime across the state,'' said Judy Yupcavage, public policy and information manager for the Pennsylvania Coalition Against Domestic Violence.
Among the Uniform Crime Report program's most serious problems:
A third of the state's 1,100 municipal police
departments routinely fail to participate in the data-reporting process, meaning the final report misses thousands of crimes. Another 15 percent or so of police departments report crimes some months but not others. In total, 2.7 million Pennsylvanians live in areas where crimes go unreported or under-reported to the state.
Officials who collect the data make little attempt to track the annual fluctuations, which leaves them unprepared to explain peaks and valleys in the data.
Little effort is made to alert the public of the report's statistical shortcomings, other than a disclaimer that reporting is voluntary and not all departments submit numbers.
These problems undermine the program's stated mission: to provide government officials and the public with information about crime in Pennsylvania and to provide law enforcement administrators with criminal statistics.
The combination of missing data and failure to disclose problems in the Uniform Crime Report calls into question its accuracy and can make the statistics misleading, according to experts.
The Pennsylvania State Police, who oversee the UCR process, defend it, saying as long as they receive data from the major metropolitan areas, they are able to track broad crime trends.
''As long as we're getting Philadelphia, Pittsburgh and the state police which are accounting for a large percentage of the crimes you're able to look at trends,'' said Jack Lewis, state police spokesman.
But the system's flaws even can derail such broad comparisons, as happened in 2001. The data excluded cities as large as Scranton, Wilkes-Barre and York.
Credible scientific studies include information about data collection problems and how those problems affect the results. But state police said such routine reporting analysis is beyond the mission of the state UCR program, which state police have overseen since 1973.
''We stand by the decisions that were made when we implemented this program that we disseminate the information as we know it, whatever data we have,'' said Sgt. Mike Troxell of the research and development unit.
The underlying problem: Pennsylvania doesn't require police to file UCR numbers and many departments say they don't have the time, resources or incentive to do so.