This is a partial transcript from "The O'Reilly Factor," June 5, 2006, that has been edited for clarity.

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BILL O'REILLY, HOST: The top story tonight: a new study about gay marriage, which says allowing homosexuals to wed actually benefits marriage in general.

Joining us now from Washington, William Eskridge, Jr., co-author of the book, "Gay Marriage for Better or For Worse: What We've Learned from the Evidence". Here in the studio, Darren Spedale, the other co-author of the book.

Mr. Spedale, let me begin with you. I have the stats. And I have gone over these stats all afternoon. And I can't really extrapolate anything from them. Where am I going wrong?

DARREN SPEDALE, CO-AUTHOR OF THE BOOK "GAY MARRIAGE": Sure. Well, I think the purpose of this book is really to shed some light on one of the big mysteries that people keep facing, which is they keep hearing about "defending marriage" and "protecting marriage," but nobody ever really tells them exactly what they're defending or protecting marriage from.

So here we have actually looked and there's — we found a lot of people who might otherwise be in favor of same sex marriage, but are concerned that there may be some terrible or negative effects if we actually allowed same sex couples to marry.

So we said, it's important to look at those countries that have actually had a form of same sex marriage now for 17 years and get to the real question, which is what really happens to society when their country allows gay couples to marry? Are these terrible effects? Do people end up marrying dolphins? Or is it really just a much more narrow issue?

O'REILLY: OK. And the conclusion you have come to, and correct me if I'm wrong, is that there hasn't been that much change.

But in the Netherlands, there has. And births outside of marriage, that's doubled. But in the rest of the countries, Denmark, Norway, Sweden, Mr. Eskridge — it's basically the same. Although, in Norway, this is very interesting, in the southern part of Norway, the more conservative part of the country, births outside of marriage much lower than the liberal northern part.

WILLIAM ESKRIDGE, JR., CO-AUTHOR OF THE BOOK "GAY MARRIAGE": Well, interestingly, Mr. O'Reilly, what we found in Denmark, which has had registered partnerships since 1989, the marriage rate had actually been falling in Denmark until '89. The divorce rate had been rising.

O'REILLY: Right.

ESKRIDGE: And the rate of non-marital births went up from 11 percent in the early '70's to over 45 percent in the late '80's. And the interesting thing is after Denmark recognized same sex unions, the marriage rate went back up. The divorce rate fell. And the rate of non-marital children stabilized. And in the last five years, it's stabilized at a lower level than in 1989.

O'REILLY: All right, Professor but...

O'REILLY: So one of the things we show in the book is that the situation from a traditional point of view actually improved in Denmark.

OK. But now I'm going to dash professor — the professor teaches at Yale. I'm going to be a wise guy student. I'm going to tell you that according to the statistics in Scandinavia, co-habitating parents, which now make up the majority of couples in some countries like Sweden, break up two to three times the rate of married parents. Is that true?

ESKRIDGE: I give you an "A", Mr. O'Reilly.

O'REILLY: Thank you, sir.

ESKRIDGE: But the point is that in Sweden, we've seen some of the same trends that we saw in Denmark. So in Sweden, the rate of marriage had been plummeting before 1994, when they adopted same sex unions. The rate of marriage has been increasing in Sweden since 1994.

O'REILLY: OK. I think what we can draw...

I think what we can draw...

O'REILLY: I think we can draw this is what I'm drawing from all of your data. The gay marriage per say, the marriage of homosexuals, doesn't really impact on straight marriage for those who want a traditional union.

But it does, Mr. Spedale, it does lead to a more libertine or permissive society in the sense that marriage itself then is de-emphasized as we see in Sweden. And more and more people cohabitate.

SPEDALE: No. I think that's not true. I think exactly we saw the opposite. And that's why these statistics are so interesting. In Denmark, Norway, and Sweden in each of those countries after they passed their gay marriage type laws, their registered partnership records, the rates of heterosexual marriage went up per capita. The rates of heterosexual divorce went down.

O'REILLY: But they're still mighty low? I mean, look...

SPEDALE: But they've changed.

O'REILLY: ...in Sweden, and Norway and the Netherlands, all right, those three countries, the United States rate of marriage is double. Double! Why?

SPEDALE: Well, I think the main point we want.

O'REILLY: Whoa, whoa, whoa. Who, why? You lived in Denmark for two years. All right? In Netherlands, Norway and Sweden, the rate of marriage is half of that in the United States. Why?

SPEDALE: A lot of couples choose to live their lives together, in permanent relationships, but they just don't get a marriage license.

O'REILLY: Why?

SPEDALE: A lot of them decide that they still want to spend their lives together, raise children. They decide that the certificate itself isn't so important.

O'REILLY: All right.

SPEDALE: But the important thing here really is the fact that we found that gay marriage in practice does not effect, and may even actually have the opposite effect...

O'REILLY: I will give you that point. I agree with both of you that that's true, that Lenny, Mary, and Squiggy doesn't have had anything to do with anybody marrying a woman, any man or a woman marrying a man.

But I will submit to you that the permissiveness and the de-emphasis on traditional marriage has affected these Scandinavian societies, Professor. I don't think there's any doubt about it.

ESKRIDGE: Mr. O'Reilly I give you another "A". But one of the reasons that the divorce rate has gone up in Scandinavia is no-fault divorce.

Same is true in the United States. One reason that the cohabitation rate has gone up in Scandinavia is that cohabitation in Scandinavia is legally supported.

We've also seen that in the United States, a statistic that's also in our book, as are the ones that you mentioned, is that the number of households raising children in the United States with a single parent is between 25 and 26 percent. In Denmark, it's between 18 and 19 percent.

O'REILLY: Right. But they're not married. That's the thing.

SPEDALE: That's right. And that's the whole crux of the issue. And I think you guys did very good research. And I don't — I think it's a very interesting book that people should read.

But I will say this. The people who oppose gay marriage, they believe the traditional family, the married man and woman are best qualified to marry children in this country. That's the overwhelming issue.

O'REILLY: Gentlemen, thanks for coming in. We appreciate it.

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