The Alabama Senate just voted for a bill that would opt the state out of funding abortions under the new federal health-care bill. Several states, including Indiana, Kansas and Texas, have moved to prohibit the government from giving tax dollars to Planned Parenthood. Nebraska legislators passed a bill requiring teenagers to get parental consent before obtaining an abortion.

These are not isolated incidents, but represent a trend. As pro-life legislation on the federal level often fails to make it out of the Republican-controlled House of Representatives, such legislation is making more headway on the state level.

Michael New says that such laws have a far-reaching effect. New,  an assistant professor of political science at the University of Alabama, has published research showing that pro-life legislation has a direct effect on reducing abortion.

New, who starts in the fall of 2011 as an assistant professor at the University of Michigan at Dearborn, spoke about how this works.

Between 1990 and 2005 the number of abortions nationally fell between 20% and 25%, depending on the data. Why?

There are several reasons why it happened. More states passed pro-life laws. No states had informed-consent laws, as they had not received constitutional protection until 1992. By 2005, 33 of the 50 states had informed-consent laws. Similarly, no states had waiting periods in effect in the early 1990s, but by 2005, 22 states had waiting periods. Finally, between 1992 and 2005, the number of states that were enforcing parental-involvement laws increased from 20 to 34.

My research found that abortion rates have declined in nearly every state, but we see the biggest declines in states like Mississippi, which has enacted many pro-life laws, and Pennsylvania, which passed a very strong-informed consent law known as the Abortion Control Act.

Are there other reasons why abortion rates might have declined?

There is some evidence that when the economy is strong abortion rates go down, and the economy was stronger in the mid 2000s than in the early 1990s. There is evidence that young people have been engaging in sexual activity less often, and sexually active young people now are more likely to use contraception. The fact that there are fewer abortion providers has also played a role as well.

Also, a shift in public opinion toward a more pro-life position probably also played a role. But it’s hard to quantify what kind of impact cultural trends have on individual choices.

How effective are parental-consent laws?

I describe parental-notice laws and parental-consent laws as “parental-involvement laws,” and they typically bring minor abortion rates down by about 15%. They have more impact on younger minors than older minors, who are more likely to either wait for their 18th birthday to have an abortion or cross the border into a state with more permissive laws.

What about laws restricting Medicaid funding for abortions?

If a state cuts off Medicaid funding, abortions consistently decline by about 10%.

The Guttmacher Institute conducted a literature review on this subject. Twenty of the 24 studies they reviewed found that public-funding restrictions reduce abortion rates. I think the reason why these laws are effective is because, by and large, these laws are self enforcing. By contrast, other pro-life laws require abortion providers to police themselves, and they may not do that very well. Laws that restrict public funding of abortion are the most effective legislative tool to cut abortion rates.

What about informed consent and the impact of sonogram images on women’s choices?

Informed-consent laws received constitutional protection in the Supreme Court’s Planned Parenthood v. Casey decision in 1992. These laws provide some combination of three things: They give women information on fetal development, information about potential public and private sources of support for pregnant women and single mothers, and give information about the health risks posed by abortion procedures.

The most effective informed-consent laws require women to make two separate trips to the abortion provider. Both Mississippi’s informed-consent law and Utah’s informed-consent law include such a provision. Pennsylvania’s law does not explicitly require two trips, but requires in-person counseling before the abortion, and that effectively means in two trips. In rural areas, two trips increase economic costs and make it less likely that the woman will have an abortion.

In recent years, a new generation of informed-consent laws has given women the option to view an ultrasound prior to the abortion. We don’t have a lot of data on the effectiveness of these laws. But I would have some concerns about any law that requires abortion providers to police themselves.

When did you begin to study the impact of pro-life legislation on abortion rates?

I started research in the fall of 2002. The 30th anniversary of Roe v. Wade was coming up, and I wanted to hit that anniversary. Unfortunately, at first, I couldn’t find anyone willing to publish the study.

Even conservative think tanks and foundations proceed with caution when dealing with abortion. They want to make sure the methodology and data are correct. I developed a relationship with the Heritage Foundation, a Washington, D.C., think tank. During the summer of 2003, they had someone recreate my whole dataset from scratch.

My results and their researcher’s results matched. Heritage then released my first study on pro-life laws in January 2004. Between 2004 and 2007, the Heritage Foundation released four of my studies on the effects of pro-life laws. The Family Research Council released another study of mine in 2008. After a very extensive peer-review process, State Politics and Policy Quarterly (SPPQ), the top state politics journal in the country, published a study of mine in March of 2011.

Why is abortion research controversial?

The pro-life movement wants to portray itself as effective, and its opponents want to portray it as ineffective.

Pro-lifers were interested in my findings and wanted me to speak at conferences and various forums. But the other side tries to discourage pro-life political and legislative efforts. In every election, the same op-eds appear arguing that pro-life efforts are ineffective because the abortion rate went up under President Reagan and down under President Clinton. Of course, correlation is not causation.

Opponents of pro-life legislation often argue that if you want to get abortion numbers down, you should spend money on welfare assistance and publicly funded contraception. But there is no evidence that either of these strategies work. I haven’t found one study analyzing actual abortion data saying that spending money on welfare or contraception pulls abortion numbers down.

Register senior editor Joan Frawley Desmond writes from Chevy Chase, Maryland.