 Evidence for a causal relationship between exposure to pornography and sexual aggression is slim and may, at certain times, have been exaggerated by politicians, pressure groups and some social scientists. Some of the debate has focused on violent pornography, but evidence of any negative effects is inconsistent, and violent pornography is comparatively rare in the real world. Victimization rates for rape in the United States demonstrate an inverse relationship between pornography consumption and rape rates. Data from other nations have suggested similar relationships. (Ferguson and Hartley 2009)