The title mostly says it all. I understand the motivation of hate crime legislation, and if it works I'm totally supportive of it. However, I'm curious if it works in practice. Are criminals really saying "well, I was totally going to commit that crime out of bigotry, but now that I face another five years for my bigotry it's no longer worth the risk"? That just seems a bit more rational then I expect from the average bigoted criminal. So I'm looking for studies that look into the efficacy of hate crime legislation and rather they successfully decrease the amount of hate motivated crimes.

When I refer to 'hate crime legislation' I'm actually asking about a specific subset of laws. I'm only interested in laws that add an additional penalty for an existing crime if it's demonstrated that this crime was primarily motivated by a hatred or bias against a group (race, sex, gender, religion, etc.) that the victim was part of. I am not asking about the legislation that would penalize someone for doing something otherwise legal if the motivation was hatred of the victims identity. So for example a law that would add additional penalty if It can be demonstrated the motive for beating someone up was their skin color would be relevant to my question, but I'm not asking about laws that prevent firing someone because they turned out to be gay since firing someone would otherwise be legal if not for the motivation of the firing.

I'm looking for peer reviewed scientific studies, not opinion or anecdote. I'm most interested in the USA perspective, but I'd be willing to accept studies done in any first world nation.