A couple weeks ago on Mad Men, Peggy got recruited to go to another, much larger ad agency. Instead of saying yes right away, she went into Don Draper's office to see if she could get a raise.

She's a copywriter, but she gets paid much less than the other copywriters, all of whom happen to be male. And so she invokes the recently passed Equal Pay Act. "It's a law now," she says. "Equal pay for equal work." Don looks at her as though she's speaking another language. "Peggy, it's not a good time," he tells her. Then he asks her if she wants a drink.

When Peggy confronts Don, it's 1963, and the median annual income for women was around 60 percent of men's. Today, it's around 77 percent—a gain, to be sure, but hardly anything to be thrilled about. While some of the so-called gender gap can be explained by the fact that women tend to work in lower-paying fields—such as education and child care (I'm going to bracket the debate about whether these deserve to be lower-paying fields at all)—there's still a five percent wage gap for male and female college graduates, even after controlling for things like age, race and ethnicity, region, marital status, children, occupation, industry, and hours worked, according to testimony given in April to the United States Joint Economic Committee. The conclusion? "It is reasonable to assume that this difference is the product of discrimination."

But it's slightly more complicated, I think, and it raises uncomfortable questions about the differences between men and women—whether they're socially determined or not. A couple years ago, there was another study that focused on men vs. women in negotiations; men, it showed, will take the initiative and ask for things like more money or a promotion, while women will wait to be asked. And this can have major repercussions:

If a 22-year-old man and a 22-year-old woman are offered $25,000 for their first job, for example, and one of them negotiates the amount up to $30,000, then over the next 28 years, the negotiator would make $361,171 more, assuming they both got 3 percent raises each year. And this is without taking into account the fact that the negotiators don't just get better starting pay; they also win bigger raises over the course of their careers.

It's hard not to look at these studies and think about anecdotal evidence from my own life. At my first job out of college, I was offered just that salary: $25,000 a year. I didn't even think about negotiating. Sure, you could argue that I wasn't exactly coming from a position of strength, as a 22-year-old college graduate with little experience who was desperate for a job. But over the years, I saw how certain people—and nearly all of them were men—were able to ask for things that I wouldn't even have thought of to ask for: Extra vacation days. Bonuses. When I was in graduate school, better teaching schedules (and better professor assignments). A few years later, I was offered another job at what I now considered a laughable salary, $35,000 a year. I countered at $65,000. We settled on $57,000, with a guaranteed raise to $60,000 after three months. And I came up with a new motto: "You don't ask, you don't get."

I bring specific salary numbers in part because women, it seems to me, are generally less comfortable discussing money than men—which also leaves us in a position of weakness. At yet another job I had (salary: $38,000), the founders of the company told us, with straight faces, that one of the bad things about unions were that everyone knew what everyone else was making. The employees all nodded solemnly, like, OMG, wow, what a horrible thing to know. Talking about money is taboo, of course! It was only later that I realized, duh! Of course they wouldn't want everyone to know what everyone else is making, because then everyone would ask for more money.

These days, when people are desperate for work and employers admittedly have the upper hand, it can seem as though we're all Peggys in a Don Draper world. But Peggy, I suspect, just might have the last word.

The Gender Wage Gap 2008 [Institute for Women's Policy Research]
Equal Pay for Equal Work? New Evidence on the Persistence of the Gender Pay Gap [AAUW]
Salary, Gender and the Social Cost of Haggling [Washington Post]