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I've only read the tipping point theory behind this.
What is the Freakonomics reasoning behind it?
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The reasoning is that people who have abortions are in the same demographics that produce criminals, and that a lower birthrate amongst these people produced less criminals. The reason it took 20 odd years after roe v wade for this to happen is that 9 year olds tend to not be very good at carjacking.
wiki on it