The claim that women make less than men is one of those claims that is true but not in the way that people want you to believe. The true part is that women earn less than men. The untrue part, and this is the piece union leaders would like you to believe, is that women with the same work history, the same educations, and working in the same fields as men earn less than men. The earnings data is quite clear that this is simply not true.

What does all this mean? It means that the (very real) male-female wage difference isn't due to gender discrimination in the workplace. At worst, it might be due to gender discrimination in schools where boys may be encouraged to go into more technical fields while girls may be encouraged to go into more social fields. But there isn't compelling evidence of discrimination there either. The evidence suggests that the reason for earnings differences is most likely personal choice. Women (on average) tend to enjoy studying and working in fields that involve human care and interaction, like social work, nursing, and elementary education. Men (on average) tend to enjoy studying and working in fields that involve mathematics and abstract reasoning, like engineering and statistics. Because jobs that involve mathematics and abstract reasoning tend to pay more than jobs that involve human interaction, you find men earning more. The reason isn't gender discrimination. The reason is differences in preferences for work and fields of study.

When a couple has children, women (on average) tend to be the ones who suspend their careers to care for the home and children. While the woman's career is in hiatus, the man is accumulating work experience. Consequently, the man often ends up earning more than the woman — again, not because of gender discrimination but because of life choices the couple makes in keeping a home and raising a family. There are many other life choices that the genders make differently that also contribute to differences in wages. For example, men (on average) tend to dislike dangerous work, like logging and deep-sea fishing, less than do women. Of course, dangerous work pays more. But this isn't because dangerous work involves men. It's because dangerous work involves danger.

All of these facts are true on average. And that's the important point. There are many women who, for varied reasons, earn more than men. Carly Fiorina, the former CEO of Hewlett-Packard, and Meg Whitman, the current CEO, are good examples. So too are Hillary Clinton, Condoleezza Rice, and Christy Walton. There are also many men who, for varied reasons, earn more than women. To answer the important question of whether employers discriminate against women, we have to compare women and men with the same educations, work histories, and fields of work. When we do that, we find that women and men earn the same.

In the end, union leaders contradict themselves. Union leaders are quick to say that greedy corporations will do whatever they can to pay employees less. This is why unions claim to support the minimum wage and employer-paid vacations. But if it is true that women earn less than men because of gender discrimination, then by the unions' own argument, we should observe these same greedy employers employing only women because women are cheaper. That they aren't should tell us that there is more to the story than union leaders would have us believe.