It’s not every day that both sides of the abortion debate celebrate the same milestone. But that’s what happened on Feb. 3, when a report was released showing that the U.S. abortion rate in 2011 had fallen to its lowest level since the Supreme Court legalized the procedure nationwide in 1973. Abortion-rights groups heralded the news as proof that wider access to contraception reduces the need for abortion. Anti-abortion activists, meanwhile, said it showed that more women are carrying unintended pregnancies to term on moral grounds.
But those are just two of many possible explanations. The authors of the study, funded by the Guttmacher Institute, an abortion-rights group whose data is widely respected, said the recession may have played a central role in the 13% decline in the abortion rate from 2008 to 2011, since women are likelier to avoid pregnancy in times of economic uncertainty. Increasing use of highly effective long-term birth control, like intrauterine devices, may also have played a part.
What’s less clear, however, is the effect of legislation. Although a record number of state-level abortion restrictions–governing everything from ultrasounds to abortion-clinic architecture–have been enacted since 2010, most took effect outside the window studied by Guttmacher researchers, who said they found no direct connection between new restrictions and the abortion rate. Rates have fallen in New York and California, for example, even though neither state has passed any new restrictions.
But even the abortion rate itself, a measure of the number of pregnancy terminations per 100,000 women of child-bearing age, does not tell the whole story. There are fewer abortions now in part because there are fewer total pregnancies. The 2012 U.S. birthrate was the lowest on record. In addition, cultural norms are shifting. More unmarried couples are living together and experiencing unplanned pregnancy, but the share of all unplanned pregnancies ending in abortion declined from 47% to 40% from 2001 to 2008. This is a sign, says Guttmacher’s director of domestic research Lawrence Finer, that “for some couples, a nonmarital birth is not as stigmatized as it used to be.”
This appears in the February 17, 2014 issue of TIME.