The causes of crime fall, to a large extent, into the category of "known unknowns." Certain factors are often associated with crime, but correlation is not causation. Take one of the major factors frequently tagged as a "root cause" of crime: poverty. Mayor Catherine Pugh, when asked why Boston had a far lower homicide rate, replied that it could not be compared with Baltimore because it is considerably more affluent. This view is, at best, a half truth. Baltimore's poverty rate is 5 percent higher than Boston's. Can that really explain why Baltimore's homicide rate is 650 percent higher?