My point is that most women do not opt for the kind of work that will make them a lot of money, so when one says that the average salary of women is this and the average salary of men is that, then you are not comparing apples with apples. You are, in fact, comparing highly paid jobs with poorly paid jobs.
I'm very curious about your source for this statement. I too worked for very little back in the 70's, and was told that the man who was my subordinate was paid more than double because he had a wife and a mortgage. On my way out the door I told my boss that, if I were earning that much I could BUY a husband. I walked down the block and was instantly hired by a competitor for much more pay. The women I know are all professionals, with careers, ambition, and so forth, looking for the best compensation they can find. Maybe "back in the day" when we were young, it may have been true that women gravitated toward secretarial or clerical positions, because that's what our mothers told us we should do while we were waiting to catch a husband.