It’s a two-way street, as I said, some have claimed to rebuke what Freakonomics says, I really looked into this probably about 2 years ago. Plenty of articles on the internet on the subject: http://www.lifenews.com/2011/06/02/freakonomics-claim-abortion-drops-crime-rates-refuted-again/
Also, what good is the Freakonomics issue if we allow criminals to come into our country unfettered? Another question.