Just how common is police misconduct? It's question that vexes researchers and journalists, and it's been a source of endless argument in the nationwide debate over policing that has erupted in recent years. The problem is, no one can definitively say. There are roughly 18,000 police departments in the U.S., and no uniform reporting of when their officers are charged with crimes.

A new database launched Tuesday is attempting to change that.

The Police Crime Database, created by Bowling Green State University professor Philip Stinson, aims to track every instance when a police officer is charged with a crime. So far the project has identified 8,006 arrest incidents resulting in 13,623 charges against police officers in the U.S. between 2005 and 2011.

Among Stinson's finding, which were first reported by Vice News Tuesday:

Police were most frequently charged with misdemeanor assault and driving under the influence.

1,219 officers were arrested for sex crimes. In those cases, more than half of the alleged victims were minors. Seventeen percent of the officers arrested for sex crimes were charged in multiple sex-related cases

Nearly a quarter of officers charged with crimes "were sued at some point during their career for federal civil rights violations, like excessive use of force or verbal harassment," Vice News reports.

359 of the charges were for forcible rape.

However, while the database is an unprecedented attempt to quantify police crime, it is far from a complete look at the issue.

The Justice Department does not track such information, and the database has to rely on media reports and Google News searches to gather information. The database does not include civil suits against officers or departments, nor does it include misconduct that did not result in criminal charges or was handled administratively.

Jonathan Blanks, a researcher at the Cato Institute who tracks police misconduct, says in an interview "we have no idea" how many cases are slipping through the cracks.

"The underlying problem is the 18,000 police agencies in this country are notoriously secretive about what data they release on discipline and officer accountability," he says. "Sometimes it's internal policies, sometimes it's state laws protecting human resources."

New York police departments, for instance, have expansively interpreted the state's privacy laws to block the release all but the most basic numbers about civilian complaints against officers. New York's highest court will soon rule on whether the NYPD can invoke the same law to hide disciplinary records on its 35,000 sworn officers, after the department abruptly stopped posting the outcomes of internal disciplinary trials last year.

Still, Blanks says the database—fully searchable by crime and location—will be a valuable resource.

"I really do think this does provide a good service where you can see what's going on and how these officers move through the criminal justice system," Blanks said. "That in and of itself shows how diligent a police department is in rooting out its own problems, and how the prosecutors decide to go forward with these cases."

Blanks cited a 2013 case where a San Antonio police officer, Daniel Lopez, was arrested after pulling a gun on his wife during a domestic dispute, sparking a standoff with a SWAT team. He had been suspended and stripped of his service weapon a month earlier after firing it inside his home. Lopez was fired from the department, but prosecutors reduced his charges to misdemeanor disorderly conduct, rather than aggravated assault with a deadly weapon.

As part of the deal, Lopez was allowed to keep his peace officer's license.