A number of researchers have argued that crude rates of crime and delinquency are a function of a population's age pyramid. That is, given constant age-specific rates, the overall or crude rate will fluctuate in concert with the proportion of individuals in age groups with differing age-specific rates. Richard Easterlin, however, has suggested that it is unreasonable to expect age-specific rates to remain constant in the face of fluctuating population distributions. Specifically, it is suggested that many social phenomena, such as crime rates, will fluctuate according to the relative size of the age cohort considered.This hypothesis is tested using offlcial delinquency statistics from the Province of Ontario, Canada, for the years 1952–81. The data suggest that Easterlin's hypothesis is, in fact, a credible one.