The abortion rate in the United States hit a three-decade low in 2011 -- and a new wave of abortion restrictions aren't necessarily the reason why.

New data published Sunday by the Guttmacher Institute shows that, in 2011, there were 16.9 abortions per 1,000 women between 15 and 44, which is a drop of 13 percent since 2008 -- and the lowest rate the nonprofit has recorded since the Supreme Court legalized abortion in its 1973 Roe v. Wade decision. The abortion ratio -- the percent of pregnancies that end in abortion -- has also declined steadily over the same time period, which you can see below.

This is down from a peak in the rate in 1980, of 29.3 abortions per 1,000 women between 15 and 44.

These decreases happened all across the country, with all but six states seeing their abortion rates drop between 2008 and 2011. The abortion rate declined 9 percent in the Northeast, 17 percent in the Midwest, 12 percent in the South, and 15 percent in the West.

The ranks of abortion providers have decreased slightly, by 4 percent, between 2008 and 2011. Most of that change is not about abortion clinics closing. The number of providers working in those stand-alone facilities only declined by 1 percent over the three-year period, meaning most of the decrease came from abortion providers who work in more general practices or in hospitals. The Midwest, notably, was the one region of the country where the number of abortion clinics increased between 2008 and 2011, by 8 percent (most of this is due to a surprisingly high number of abortion clinics opening in Iowa, increasing their ranks from 10 in the state to 17).

Taking all of that together, researchers don't think it's the 44 abortion restrictions passed between 2008 and 2011 that have led to the decrease in the abortion rate. Instead, they point a finger at more widespread contraceptive use. The use of long-acting reversible contraceptives like intra-uterine devices which tend to be more effective, for example, has more than quadrupled over the past decade.

This isn't to say that state laws might not show up in future research: The biggest wave of abortion restrictions happened from 2011 through 2013, so they aren't really captured in this particular study (many laws that passed in 2011 didn't take effect until the end of that year or beginning of the next). So in future research, those could show up. But right now, it doesn't seem that restrictions are driving the lower abortion rate.