Yes, this would be my first suspicion too, especially for a comparison with the 1990s. > For instance, the peak in leaded gasoline use in the late 1970's corre

Yes, this would be my first suspicion too, especially for a comparison with the 1990s. > For instance, the peak in leaded gasoline use in the late 1970's corresponds to a peak in aggravated assault rates in the late 1990's in urban areas across the United States. https://en.wikipedia.org/wiki/Lead_poisoning#Violence https://en.wikipedia.org/wiki/Lead_poisoning#Violence