Surely it can’t be true. President Kennedy signed the Equal Pay Act in 1963. The very next year Congress passed Title VII of the Civil Rights Act of 1964, which banned sex discrimination at work. Yet nearly fifty years later, women still make less than men.

We live today in a world where women run Fortune 500 companies, sit on the Supreme Court, and push back the frontiers of knowledge. We live during a time when more young women than men hold bachelor’s degrees, and when women make up almost half of all new law school graduates. Given all our progress, there must be some explanation behind the fact that women still lag behind men when it comes to pay equity.

Earlier this week, the Paycheck Fairness Act failed to advance in the Senate, triggering a new round of conversation about the pay gap and what the numbers really mean. Research shows that even though equal pay for women is a legal right, it is not yet a reality. Despite the evidence, myths that women’s choices or other legitimate factors are the “real” cause of the pay gap persist. So does confusion about how to measure the gap and what figures to use. That’s why today, we are going to bust a few myths.

MYTH: Saying women only earn 77 cents on the dollar is a huge exaggeration – the “real” pay gap is much smaller than that (if it even exists).

REALITY: The size of the pay gap depends on how you measure it. The most common estimate is based ondifferences in annual earnings (currently about 23 cents difference per dollar). Another approach uses weekly earnings data (closer to an18 or 19 cents difference). Analyzing the weekly figures can be more precise in certain ways, like accounting for work hours that vary over the course of the year, and less accurate in others, like certain forms of compensation that don’t get paid as weekly wages. No matter which number you start with, the differences in pay for women and men really add up. According to one analysis by the Department of Labor’s Chief Economist, a typical 25-year-old woman working full time would have already earned $5,000 less over the course of her working career than a typical 25-year old man. If that earnings gap is not corrected, by age 65, she will have lost hundreds of thousands of dollars over her working lifetime. We also know that women earn less than men in every state and region of the country, and that once you factor in race, the pay gap for women of color is even larger.

MYTH: There is no such thing as the gender pay gap – legitimate differences between men and women cause the gap in pay, not discrimination.

REALITY: Decades of research shows a gender gap in pay even after factors like the kind of work performed and qualifications (education and experience) are taken into account. These studies consistently conclude thatdiscrimination is the best explanation of the remaining difference in pay. Economists generally attribute about 40% of the pay gap to discrimination – making about 60% explained by differences between workers or their jobs. However, even the “explained” differences between men and women might be more complicated. For example: If high school girls are discouraged from taking the math and science classes that lead to high-paying STEM jobs, shouldn’t we in some way count that as a lost equal earnings opportunity? As one commentator put it recently, “I don’t think that simply saying we have 9 cents of discrimination and then 14 cents of life choices is very satisfying.” In other words, no matter how you slice the data, pay discrimination is a real and persistent problem that continues to shortchange American women and their families.

MYTH: But the pay gap is not my problem. Once you account for the jobs that require specialized skills or education it goes away.

REALITY: The pay gap for women with advanced degrees, corporate positions, and high paying, high skill jobs is just as real as the gap for workers overall. In a recent study of newly trained doctors, even after considering the effects of specialty, practice setting, work hours and other factors, the gender pay gap was nearly $17,000 in 2008. Catalyst reviewed 2011 government data showing a gender pay gap for women lawyers, and that data confirms that the gap exists for a range of professional and technical occupations. In fact, according to a study by the Institute for Women’s Policy Research that used information from the Bureau of Labor Statistics, women earn less than men even within the same occupations. Despite differences in the types of jobs women and men typically perform, women earn less than men in male dominated occupations (such as managers, software developers and CEO’s) and in those jobs commonly filled by women (like teachers, nurses and receptionists). In a recent review of 2010 Census data, Bloomberg found only one of 285 major occupations where women’s median pay was higher than that of men – personal care and service workers. Because the data showed a particularly large pay gap in the financial sector, Bloomberg suggested that for women on Wall Street, shining shoes was the best way to earn more than the men.

MYTH: Women are responsible for the pay gap because they seek out flexible jobs or choose to work fewer hours. Putting family above work is why women earn less.

REALITY: Putting aside whether it’s right to ask women (or men) to sacrifice financially in order to work and have a family, those kinds of choices aren’t enough to explain away the gender pay gap. The gender gap in pay exists for women working full time. Taking time off for children also doesn’t explain gaps at the start of a career. And although researchers have addressed various ways that work hours or schedule might or might not explain some portion of the wage gap, there may be a “motherhood penalty.” This is based on nothing more than the expectation that mothers will work less. Researchers have found that merely the status of being a mother can lead to perceptions of lowered competence and commitment and lower salary offers.

MYTH: We don’t need to do anything, the gender pay gap will eventually go away by itself.

REALITY: It has been nearly fifty years since Congress mandated equal pay for women, and we still have a pay gap. There is evidence that our initial progress in closing the gap has slowed. We can’t sit back and wait decades more. Just this year the Department of Labor launched an app challenge, working to give women the tools they need to know their worth. My office continues to increase its enforcement of requirements that federal contractors pay workers without discriminating on the basis of race or gender. And we are teaming up with other members of the National Equal Pay Task Force to ensure a coordinated federal response to equal pay enforcement. You can read more about our work on equal pay here.

The pay gap isn’t a myth, it’s a reality – and it’s our job to fix it.

Editor’s Note: The author, Dr. Pamela Coukos is a Senior Program Advisor at the Department of Labor’s Office of Federal Contract Compliance Programs.