Sex-Ratios and Rape

Here's an interesting article arguing that an excess number of males in an area drives more marginal men to compete with other men with high-risk strategies like rape. The graph below shows the correlation between a surplus of men and the rate of rape. The size of the relationship--.42--is moderate. Race is a strong state-level predictor of violence crime, but percent black should also be associated with a surplus of women. It would be good to see the sex-ratio/rape correlations with race adjusted for.