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:

• In 1992, virtually no states were enforcing informed consent laws.By 2000, 27 states had informed consent laws in effect.
• In 1992, no states had banned or restricted partial-birth abortion. By 2000, 12 states had bans or restrictions in effect.
• In 1992, only 20 states were enforcing parental involvement statutes.By 2000, 32 states were enforcing these laws.

But we don't have to throw up our hands. As New points out, there's a built-in way to judge whether the laws are making a difference. In some states, courts have struck down the pro-life legislation in question; in others, obviously, it has become law. By comparing the two groups, we can find which has a greater effect: changes in values or changes in law. If it's a shift in values, then states that have had their pro-life laws nullified will show a decline in abortion similar to states where the laws are allowed to take effect.

I'll have to refer you to Professor New's paper for the technical explanation of how he did it, but the bottom line is this: The laws made a real difference. As New puts it:

Overall, this research finds that value shifts have little impact on the incidence of abortion. Conversely, enacted legislation results in statistically significant reductions in abortion rates and ratios. This provides even more evidence that state pro-life legislation has been effective in reducing the number of abortions in a given state. Furthermore, it provides additional support for the idea that pro-life legislation was partly responsible for the substantial decreases in abortion rates and ratios during the 1990s.

Several positive conclusions can be drawn from this. One is that pro-lifers shouldn't let their discouragement over Roe v. Wade's 33-year history as settled law keep them from pursuing laws that will at least cut down on the number of abortions. It shouldn't be "all or nothing."

And since these laws work, pro-lifers should make every effort to make them as widespread as possible. This shows the good that people who live "outside the Beltway" can accomplish when they change things for themselves, rather than wait passively for somebody in Washington to do it for them.

Just think: Working with their state officials, citizens around this great nation of ours have helped cut down on the number of abortions. No matter what you think of how Ayotte v. Planned Parenthood was decided, that's a clear-cut victory for life. Let's pray there are many more.

Rebecca Hagelin is a vice president of The Heritage Foundation and the author of Home Invasion: Protecting Your Family in a Culture that's Gone Stark Raving Mad.