How women respond to these closings, however, is another story.

We do not have large enough surveys to discern behavior in different states or to track how it has changed over time — and in any case, people may not feel comfortable sharing the truth in a survey.

Google searches can help us understand what’s really going on. They show a hidden demand for self-induced abortion reminiscent of the era before Roe v. Wade.

This demand is concentrated in areas where it is most difficult to get an abortion, and it has closely tracked the recent state-level crackdowns on abortion.

In 2015, in the United States, there were about 119,000 searches for the exact phrase “how to have a miscarriage.” There were also searches for other variants — “how to self-abort” — and for particular methods. Over all, there were more than 700,000 Google searches looking into self-induced abortions in 2015.

For comparison, there were some 3.4 million searches for abortion clinics and, according to estimates by the Guttmacher Institute, there are around one million legal abortions a year.

The 700,000 searches included about 160,000 asking how to get abortion pills through unofficial channels — searches like “buy abortion pills online” and “free abortion pills.”

There were tens of thousands of searches looking into abortion by herbs like parsley or by vitamin C. There were some 4,000 searches looking for directions on coat hanger abortions, including about 1,300 for the exact phrase “how to do a coat hanger abortion.” There were also a few hundred looking into abortion through bleaching one’s uterus and punching one’s stomach.

Search rates for self-induced abortion were fairly steady from 2004 through 2007. They began to rise in late 2008, coinciding with the financial crisis and the recession that followed. They took a big leap in 2011, jumping 40 percent. The Guttmacher Institute singles out 2011 as the beginning of the country’s recent crackdown on abortion; 92 provisions that restrict access to abortion were enacted. There was not a comparable increase in searches for self-induced abortions in Canada, which has not cracked down.

Of course, we cannot know from Google searches how many women successfully give themselves abortions, but evidence suggests that a significant number may. One way to test this is to compare abortion and birth data.

In 2011, the last year with complete state-level abortion data, women living in states with few abortion clinics had many fewer legal abortions.

Compare the 10 states with the most abortion clinics per capita (a list that includes New York and California) to the 10 states with the fewest abortion clinics per capita (a list that includes Mississippi and Oklahoma).

Women living in states with the fewest abortion clinics also had more live births. However, the difference was not enough to make up for the lower number of abortions. There were six more live births for every 1,000 women of childbearing age.

In other words, there appear to have been some missing pregnancies in parts of the country where it was hardest to get an abortion. Self-induced abortions could be playing a role, although more research must be done on rates of pregnancy and unintentional miscarriage in different regions.

One recent survey in Texas also reported a surprisingly high number of attempted self-induced abortions. It found that 4.1 percent of Texas women were sure or suspected that their best friend had tried a self-induced abortion. The researchers asked about best friends because women may not feel comfortable admitting their own attempts. In fact, so much secrecy surrounds abortion today that it is likely that many women would not know that their closest friends had tried a self-induced abortion.

According to another survey, which was published in Sociological Science, 34 percent of Americans who have been involved in an abortion — either they had one or they were the potential father — disclosed this to no one else. Among those who did tell others, they told an average of 1.2 people. We can expect that people would be even less likely to inform friends and family members about self-induced abortions.