Unanimous verdicts by the Supreme Court are rare. Yet, last week, we witnessed one—and in an abortion case, no less.

Ayotte v. Planned Parenthood concerned a law that New Hampshire passed in 2003 requiring minors to give parents 48-hours notice before an abortion. Although the law contains some restrictions (e.g., the requirement was waived if a judge decided that the minor in question was mature enough to give informed consent), it lacked an explicit health exception. That’s been the sticking point in past parental-notification cases, so the justices told a lower court to decide whether the New Hampshire legislature would have passed the law if a health exception had been included.

Neither side in the abortion debate was entirely happy with the verdict. But it raises an interesting question: Is such pro-life legislation effective? Do parental-notification laws, partial-birth abortion bans and informed-consent laws make a difference? According to a new Heritage Foundation paper, the answer is yes.

This isn’t merely the author’s opinion or a case of wishful thinking. Michael New, an assistant professor in political science at the University of Alabama, carefully and scientifically analyzed the numbers using a methodology that’s included with the paper. His research began with these two facts: During the 1990s, the number of abortions dropped by around 18 percent (after rising in the 1970s and ’80s) even as the amount of pro-life legislation mentioned above—parental-notification laws, etc.—increased substantially: