DR. HEIDI HARTMANN, INSTITUTE FOR WOMEN’S POLICY RESEARCH: You’re welcome. It’s a pleasure. Thank you.

MADDOW: I know that you at the women ‘s — Institute for Women’s Policy Research , you have done some of the most important and most highly publicized work on this issue. Is there any way that the idea of a gender- based disparity is something that depends on how you look at it? Is this something other than a blunt truth about the American economy ?

HARTMANN: Well, I mean, you obviously have by far the better part of the argument. You’ve got the Census Bureau and I might mention, the Bureau of Labor Statistics agreeing with you. Oh, also, I could mention, the U.S. General Accountability Office . I think what the issue is for the Republicans is that they believe that that’s not — no matter how big the wage gap is almost none of it is due to discrimination. And, of course, these numbers from BLS and Census Bureau are not really talking about discrimination. But the GAO study that I just mentioned did. They said that even when you put everything you can possibly think of in the regression equations, the statistical analyses to try to make that gap go away, you can’t explain at least 20 percent of it. Now, most other studies place the part you can’t explain as a quarter to a half. So, a large part of the gap probably is due to discrimination. But that seems to be what the debate is. And, you know, when you ask can the Republicans convince women they don’t live in the real world ? Probably not, because almost every survey that’s ever been done of working women , when you asked them about their job, like 95 percent say my biggest problem on the job is lack of equal pay .

MADDOW: In terms of just making it very clear, what you were talking about there about doing a statistical regression analysis on these things, controlling for other factors — I spent a long time going through the Republican side of this argument today just trying to understand how you could look at these very blunt numbers and come up with the opposite truth. What you’re saying basically is when you control for things like the number of hours worked, you’re still getting a gender based pay disparity that is not explained by working a different number of hours?

HARTMANN: Right. Exactly. I mean, Alex seemed to believe if you put in working a different number of hours that would explain it. No, far from it. If you look at all workers and male and female in the economy, we know, let’s say, during the childbearing years, about a third of women may be working part time . So count part time . Count how much women work. OK. I’m working part time . Only making $400 a week. Compare it to all the men, more of whom are working full time . You still get a wage ratio of 72 percent. So that means that that 77 percent isn’t going to move very much if you suddenly remove the people where the men are working 44 and the women are only making 40. No. The number of hours explains a very small part of it. I mean, these regression analysis , they include occupation . They include your education, number of years of experience, maybe sometimes marital status, number of children — just about anything you can think of. And you cannot make the whole gap go away. So there is discrimination. Now, those studies aren’t even in a way counting the sex segregation that you opened your presentation with this evening. Those studies try to hold occupation constant. You have the data up there occupation by occupation . We have some equal occupations . You mentioned police officers and sheriffs. Women are only like 1 percent behind there. Amazing. But you go to financial managers, they’re 26 percent behind. So, it is different within each occupation . But maybe why women don’t go into police as much and go into nursing more is also discrimination. So, even the exercise of trying to decide how much of wage gap is due to discrimination and how much isn’t is — that’s open to interpretation. That’s why in Canada , for example, when they talk about the wage gap between women and men, they would use a number comparable to that 72 percent figure I gave you. They would use a number that says, well, look, at how much difference men and women earn in the labor market. I mean, if we believe men and women are equally competent, equally capable, also have to live and eat and support their families, we should be wanting a society where that gap is zero, where a man and woman are making the same amount.

MADDOW: How to get to zero seems like where — that’s where I thought we were on policy . Everybody agreed there was a gap, we’re trying to get to zero, let’s fight about how we all get there, with all the ideological biases and all the different places we come from. Instead to be denying that the gap is there has blown by mind. Dr. Hartmann , founder and president of the Institute for Women ‘s Police Research thank you very much for joining us and helping us understand this. I really appreciate it.

HARTMANN: You’re welcome.

MADDOW: All right. General Motors is alive and Osama bin Laden is dead — all thanks to Mitt Romney , turns out. Exactly how that is possible, coming up.