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According to a new, comprehensive report by the Guttmacher Institute released on Monday, the abortion rate in 2011 was 16.9 per 1000 women. That's the lowest rate since Roe v. Wade. In 1981, there were 29.3 abortions per 1000 women. Both supporters and opponents of abortion rights agree that the decline is a great thing, but they don't agree on why it's happening.

Guttmacher, a pro-choice think tank, did not fully investigate why the rate has declined. But the report indicates that increased use of long-term birth control methods like IUDs, especially among young women, contributed to the declining rate. The report also points out that the troubled economy is a factor, since couples are more likely to be careful with birth control during a recession.

The report also concludes that anti-abortion laws had a minimal effect on the declining rate, because most of them took effect in 2011 or later. For example, Texas' infamous abortion restrictions (including a 20-week abortion ban and higher standards for clinics) were signed into law by Gov. Rick Perry in July 2013. Texas clinics began closing in October, and Planned Parenthood is still in the process of contesting the law. There wasn't a decrease in abortions in 2011 because of a state law passed in 2013. In fact, the states that saw big declines in abortion rates have more liberal abortion laws, like California and New York.