The authors of the study, Rachel Jones and Jenna Jerman, didn't probe reasons for the decline. But they observe that the period of time for the study was 2008-2011, before the unprecedented surge of new state-level abortion restrictions that began in the 2011 legislative session.
"With abortion rates falling in almost all states, our study did not find evidence that the national decline in abortions during this period was the result of new state abortion restrictions. We also found no evidence that the decline was linked to a drop in the number of abortion providers during this period," said Jones. "Rather, the decline in abortions coincided with a steep national drop in overall pregnancy and birth rates. Contraceptive use improved during this period, as more women and couples were using highly effective long-acting reversible contraceptive methods, such as the IUD. Moreover, the recent recession led many women and couples to want to avoid or delay pregnancy and childbearing."