Abortion in the United States has decreased to record low levels, a decline that may be driven more by increased access to contraception and fewer women becoming pregnant than by the proliferation of laws restricting abortion in some states, according to new research.

“Abortion rates decreased in almost every state and there’s no clear pattern linking these declines to new restrictions,” said Elizabeth Nash, senior state policy manager at the Guttmacher Institute, which issued the findings in a report and policy analysis on Wednesday . The institute, which supports abortion rights, periodically compiles abortion data by surveying hospitals and abortion clinics, and by reviewing information from health departments and other sources.

The institute estimated that there were about 862,000 abortions in 2017, nearly 200,000 fewer than in 2011. The abortion rate — the number of abortions per 1,000 women of reproductive age — dropped to 13.5 in 2017 from 16.9 in 2011, the lowest rate since abortion became legal nationwide in 1973.

The report suggests that one reason for the decrease might be the growing use of long-term contraceptive methods, like intrauterine devices and implants, which are now covered by insurance under the Affordable Care Act. Birthrates have also declined.