A new report says the abortion rate in the U.S. has fallen to its lowest point since 1973, the year the Supreme Court’s Roe v. Wade decision legalized most abortion nationwide. According to the Guttmacher Institute, there were fewer than 17 abortions per 1,000 women in 2011, a 13 percent decline in recent years. The institute did not study the reasons for the drop but said it was likely caused by the effectiveness of new forms of contraception.