Most escape me right now but I do recall something that bothered me... She implicity uses stereotypes of African American behvariour and how they change over time as an indicator of the actuall change in violent behaviour.

I'm sure it correlates somewhat, but considering how much stronger changes in wider society where and how much people's interests regarding what it was best to have other people belive about Black behaviour changed over time I don't think you can base an argument on this either way.