The big question for public health researchers is: Why? What was different in 2008, that might have lead to this downtick in abortions?

The answers seem to have less to do with economic trends, as some have suggested, and potentially more about the more effective contraceptives women are increasingly using.

The CDC data can tell us a bit of this story. Alongside the drop in the overall number of abortions, the agency also found a decline in the abortion ratio. That figure measures the number of pregnancies terminated for every 1,000 live births. That number dropped too, from 232 in 2008 down to 227 in 2009, a 2 percent decrease. That suggests that the story here isn’t just about fewer pregnancies. We can see in the data that the decisions women make after becoming pregnant are playing a role, with more deciding to continue with the pregnancy rather than terminate. 

Figuring out the other drivers is a little bit trickier. It would be easy to point to the wave of abortion restrictions that swept through state legislatures in 2011 — except that this data come from 2009, when those new laws weren’t yet in place. 

Some academics have suggested that it might be the recession: Americans have gotten more careful with their family planning as budgets have become squeezed.

“They stick to straight and narrow . . . and they are more careful about birth control,” said Elizabeth Ananat, a Duke University assistant professor of public policy and economics who has researched abortions, told the Associated Press.

The research, however, suggests that the economy actually has a relatively small impact on the abortion rate, and one that works in the opposite direction of what’s suggested above.