Temporal clustering of homicide among urban 15- to 24-year-old white and black Americans.

Temporal clustering of homicides among 15- to 24-year-old black and white Americans was studied in 22 heavily urbanized counties in the United States from 1979 through 1985. Thirty-eight million people, including 37% of black Americans and 14% of white Americans, lived in these densely developed countries. The pattern of white male homicide deaths was cyclical--that is, statistically significant excesses were observed on weekends and on national holidays. The pattern of black male homicide deaths was much less cyclical. But homicide deaths of black males were disproportionately likely to occur in a pattern of single days with multiple homicides as well as in periodic spikes, lasting less than a week, during which many homicides occurred. Implications for research and policy are discussed.