Here's why:

Knowing the city in which a person lives reveals next to nothing about his or her crime risk, especially when compared with genuine risk factors such as age and lifestyle. The young and people who spend their evenings outside of the home are at far greater risk than the elderly and homebodies.

The neighborhood you live in also matters. In all cities, serious crime is disproportionately concentrated in a handful of high-risk neighborhoods. Differences in crime rates are far greater within cities than between them. And the rankings give equal weight to crimes of vastly different seriousness and measurement error. People don't want their car stolen, but most people would prefer losing their car to losing their life in a homicide.

Cities differ in the degree to which their citizens report crimes. We do not know how much of the difference between any two cities' crime ranks is real and how much reflects measurement error.

'City' vs. 'suburb'

Cities also differ in other ways that have nothing to do with their crime risk but can greatly affect their ranking. Pure geographic happenstance — the location of the boundary line separating "city" and "suburb" — is one. Some central cities are geographically small and do not include as many middle-class areas as do larger central cities. If they did, the added population would lower their crime rate.

St. Louis, where I live, is less than 62 square miles in a metropolitan area of 3,322 square miles and contains only 13% of the area population. Washington is only 61 square miles in a metropolitan area of 6,509 square miles and contains only 12% of the metro population. In contrast, well over half of the residents in the Memphis metro area live in the central city, which covers about 280 square miles.

Crime equation

A city's crime rate equals the number of crime victims (the numerator) divided by the city population (the denominator). So if a Bethesda, Md., resident is a victim of crime in Washington, he is added to the numerator but not the denominator in calculating Washington's crime rate. This circumstance artificially inflates the crime rate in communities where the central city's population is dwarfed by that of the suburban areas.

For all these reasons, if crime rates are to be compared at all, the comparisons should be among metropolitan areas, not central cities. Doing so can change the picture dramatically. St. Louis, second in crime among central cities according to the new city rankings, places 120th in crime among the nation's metropolitan areas.

The FBI, which compiles the police data that are misused in crime rankings, has long understood the distortions inherent in comparisons of city crime rates. This year, the FBI has on its website a "Caution Against Ranking." It states: "These rough rankings ... lead to simplistic and/or incomplete analyses that often create misleading perceptions adversely affecting communities and their residents."

The FBI is right. Crime rankings tell us little about how safe we are, but the rankings themselves can hurt. Businesses think twice about relocating to "dangerous" cities. Organizations think twice about holding conventions there. Families think twice about visiting. Suburban residents needlessly fear the city. Crime rankings make no one safer. They should be ignored.

Richard Rosenfeld is Curators Professor of Criminology and Criminal Justice at the University of Missouri-St. Louis.