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Beware of data

March 1, 2009

Beware of data | fedgazette March 2009 | Federal Reserve Bank of Minneapolis

The Uniform Crime Report includes four types of violent crime: murder/nonnegligent manslaughter, forcible rape, robbery and aggravated assault, and three types of property crime: burglary, larceny-theft and motor vehicle theft. (Arson is included in UCR data in a more limited fashion.) In 2007, there were 1.4 million reported violent crimes. Aggravated assaults accounted for 61 percent of them, robbery for 32 percent, rape for 6 percent and murder for 1 percent. There were 9.8 million reported property crimes, of which burglary accounted for 22 percent, larceny-theft for 67 percent and motor vehicle theft for the remaining 11 percent.

While the database is impressive, it is also flawed. Scholars recognize that it significantly undercounts actual crime levels because many crimes are not reported to law enforcement officials. Assaults and rapes may not be reported because the victim knows the perpetrator and fears retribution. Larcenies may seem too insignificant to report, given that authorities are unlikely to do much to solve, say, a bike theft. Moreover, the FBI has a hierarchical recording system: If a victim is assaulted with a weapon and then his or her car is stolen, only the more serious offense—aggravated assault—is recorded. And local authorities may undercount reported offenses in order to convey a sense of success in fighting crime.

To redress these weaknesses, the Bureau of Justice Statistics has created another database, the National Crime Victimization Survey, which surveys individuals and households across the country, asking if they’ve been victims of crime over the past six months, and if so, collecting information about those crimes. The numbers of reported crimes are far higher in the NCVS data than in the UCR data, especially for violent crimes. A 1995 comparison found that when the UCR reported 12.2 million property crimes, the NCVS reported 32 million; the UCR reported 1.9 million violent crimes compared with the NCVS tally of nearly 11 million. Trends have been similar, however.

Douglas Clement