Why the NCS and the UCR Crime Index Appear Discrepant as Indicators of Trends in Crime

Abstract

The correct but imprecise belief that the NCS and the UCR measure trends in crime has helped foster the impressions of discrepancies between the two series. Given that both systems measure “Crime,” the expectation is that the two series should track each other over time. In fact, the NCS and UCR attend by design to two different, although overlapping, sets of crime events. Naive comparisons of trends in the two series often have failed to identify the components of the crime problem common to both and therefore involved comparisons of the incomparable. Consequently, impressions of discrepancy have been created where no consequential inconsistency existed.