This was a claim made by Mika Brzezinski recently on "Morning Joe", MSNBC's morning program of news commentary. The basis for the claim is that women, on average, are paid 77% as much as men are, on the average. Assuming this is true, it in no way support's Mika's ridiculous claim.
First of all, equal pay for equal work has been the law for a long time now, and seems to be widely accepted. Any employer who does what Mika alleges would be in severe hot water legally.
Mika is a competent journalist, but she has her head way up her you-know-what on this issue. Studies have shown that, even among couples who are committed to sharing housework equally, once the first child is born, the equality is out the window, as the female takes vastly more responsibility for the child than the male. Obviously, this means the female spends less of her time and energy on her career, compared to men.
Another stat which is pertinent is one I heard many years ago, and never refuted, which is that never-married men and never-married women get paid about equally. This supports the notion that the problem is not any workplace discrimination, but rather, different choices that men and women make as to their priorities vis a vis family vs. career.
Choices of careers between men and women have a large role here also. Women tend to pick lower-paying jobs for their careers. Relative to men, there are very few women computer engineers, for example. How many women brain surgeons and rocket scientists are there?
By using the word "counterparts", Mika implies that women are paid less for the same work as men. Nothing could be further removed from the truth.