Abortion is in decline.

In a report issued last month, the U.S. Centers for Disease Control and Prevention found that the number of abortions among women ages 15-44 dropped by 24% in the most recent 10-year window for which there is data (2007 through 2016), and the abortion rate — the number of abortions per 1,000 women — fell 26%.

These results track closely with the results of research conducted by the Guttmacher Institute, an organization that advocates for abortion rights and surveys a different set of providers. Guttmacher's figures show the abortion rate trending steadily downward from 1981, when it peaked at 29.3 per 1,000 women, to 13.5 in 2017. That's a 54% drop in 36 years.

That's good.

Even those of us who are ardent supporters of abortion rights recognize that unintended, unwanted or medically fraught pregnancies are distressing, and that terminating them is emotionally complicated.

Better still is evidence that suggests the reason abortion is in decline is because unintended pregnancy is in decline — better and more responsible use of improved contraceptive methods — and not because of the spread of state laws designed to make legal abortions more difficult to nearly impossible to obtain.

If the drop in the number of abortions was the result of laws that coerced women to carry their pregnancies to term against their will or even of successful proselytizing by foes of abortion rights, you'd expect to see a rise in the overall birthrate. But in fact, a National Vital Statistics System report issued last month shows U.S. birthrates have been trending downward since the late 1990s, and in 2018, birthrates among supposedly sexually irresponsible teens hit a record low of recent decades, down 72% from their peak in 1991.

My thought was that these positive developments might be having the unintended effect of diminishing political support for abortion rights. I know that part of the reason I have always backed abortion rights is that, coming into young adulthood in the late '70s and early '80s, I knew many young women who had abortions — women who believed that carrying an unintended pregnancy to term would derail their lives; women of great character who did not choose abortion lightly but who generally went on later to have children and careers.

Conventional wisdom is that familiarity breeds support. It's widely thought that the gay rights movement advanced as rapidly as it did because as more and more LGBTQ people publicly acknowledged their sexuality, more and more straight people realized that gay people were their co-workers, neighbors, friends, relatives and siblings, not "the other," and deserved rights and respect.

So as abortion rates continue to decline, fewer and fewer people will have a personal connection to the issue and it seems logical that support will wane.

I found only two polls to shed light on this supposition. One was a 1989 New York Times/CBS News survey that found a 19 percentage point gap (58% to 39%) between support for legal abortion among those who knew a woman who'd had an abortion and those who didn't. The other was a Pew Research Center poll in August that found a 7 percentage point gap (64% to 57%).

"We have heaps of anecdotal evidence that knowing someone who has had an abortion — especially a close relative like a mother, sister, girlfriend or aunt — tends to make people more pro-choice," said Eric Scheidler, executive director of the Chicago-based Pro-Life Action League, when I asked him about this. Though he said he had no other survey data on the point, "the pro-life movement acts on the belief that this is the case."

But for whatever reason, polls taken this year show political support for abortion rights has not fallen along with abortion rates.

An ABC News/Washington Post poll released in July found 27% support for the idea that abortion should be "legal in all cases " — the highest in the history of the poll dating back to 1996. Add in the "legal in most cases" responses and the total favorability number was 60%, again the highest in the history of the poll. Support for "illegal in all cases" was at 14%, a 12-year low.

A Pew Research Center poll released in August found even slightly higher support — 61% total support for legal abortion in all (27%) or most (34%) cases. Pew also found 70% opposition to overturning Roe v. Wade, the 1973 Supreme Court ruling that established abortion as a constitutional right in most cases, up from 63% opposition in 2013.

An NBC News/Wall Street Journal poll released in June found 34% support for the idea that abortion should be "legal in all cases" and another 22% of respondents saying the procedure should be "legal most of the time," a 56% level of support that marked "a record high for the survey," according to NBC.

A Reuters/Ipsos poll released in May found 58% support for allowing abortion in most or all cases, up from 50% when Reuters/Ipsos asked the same question just 10 months earlier.

A Gallup poll released in June found 52% of respondents identifying as "pro-choice" (in favor of abortion rights) and 43% identifying as "pro-life" (opposed to abortion rights). It was the highest number since 2006, though "similar to the findings when the question has been asked this way since 2001," Gallup reported.

Who knows all the reasons why. But a solid majority of Americans seem to be standing up for abortion rights, even in the abstract, against the legal onslaught from the minority that would deny women those rights.

That's also good.

Eric Zorn is an op-ed columnist for the Chicago Tribune.