News that Cleveland’s poverty rate is the worst in the nation--and rising--has elevated the community’s concern about conditions in the city. But a closer look at the way poverty rates are calculated suggests that all the possible causes of Cleveland’s ranking have not been fully understood.

Cleveland’s employment growth has lagged the nation’s for nearly 15 years, a fact that is often blamed on the kinds of industries that are here—either the area is burdened with too much manufacturing, or it has failed to attract enough high-tech industries. But an analysis shows little...