NEW YORK — The number and rate of abortions across the United States have plunged to their lowest levels since the procedure became legal nationwide in 1973, according to new figures released today.

The report from the Guttmacher Institute, a research group that supports abortion rights, counted 862,000 abortions in the U.S. in 2017. That’s down from 926,000 tallied in the group’s previous report for 2014, and from just over 1 million counted for 2011.

Guttmacher is the only entity that strives to count all abortions in the U.S., making inquiries of individual providers. Federal data compiled by the Centers for Disease Control and Prevention excludes California, Maryland and New Hampshire.

The new report illustrates that abortions are decreasing in all parts of the country, whether in Republican-controlled states seeking to restrict abortion access or in Democratic-run states protecting abortion rights. Between 2011 and 2017, abortion rates increased in only five states and the District of Columbia.

One reason for the decline in abortions is that fewer women are becoming pregnant. The Guttmacher Institute noted that the birth rate, as well as the abortion rate, declined during the years covered by the new report. A likely factor, the report said, is increased accessibility of contraception since 2011, as the Affordable Care Act required most private health insurance plans to cover contraceptives without out-of-pocket costs.