I’ve been thinking about the gender income gap recently and there is an idea that popped into my head. I’m not claiming it is true, but I was hoping I could get some feedback and maybe start a discussion. Without further ado, here is the model:
There are 2 types of jobs: Blue collar and white collar. White collar jobs require a college education, (which is itself expensive) blue collar jobs do not. Your income in blue collar jobs will depend upon your “physical ability”. Your income in white collar jobs will depend upon your “mental ability”. Men and women are distributed in a comparable manner on the mental ability scale. However, men have an advantage on the physical ability scale. Mental and physical ability are not correlated. Blue collar jobs pay on average less than white collar jobs. If you subtract the cost of the college education, there is substantial overlap in the returns of white and blue collar jobs.
So let’s crank through the model and see what happens. If you have low mental ability, you get a blue collar job. If you have high mental ability, you go to college and get a white collar job. Now let’s imagine you have middling mental ability. If you have high physical ability, the blue collar job will give you a higher return once you factor in the cost of college. If you have low physical ability, the white collar job will give you a higher return.
So what would that mean for a gender income gap? Well, since men are more likely to have high physical ability than women, the middling mental ability men will become blue collar workers while the middling mental ability women will become white collar workers. So if you look at the income distribution and control for education, women will have a lower average income in both blue and white collar jobs (no college and college) since the average woman in both groups has a lower level of the demanded ability.
This idea was sparked by the fact that women are now more educated than men in many fields. Unless women and men have different ability distributions, that means the mean ability of college women has to be lower than the mean ability of college men. The why that would be the case was provided by an article I read regarding longshoremen. You can make a lot of money with that kind of a job. But it requires physical strength that is much more common among men than women.
It’s quite possible I’m not the first person to think of something like that. I also don’t have empirical evidence and I’m not sure how this story could be tested. Finally, even if my model is correct, I doubt that’s the whole story. I hope I get some feedback.
PS: Before this comes up. I’m not saying that women are less intelligent than men or that blue collar workers are stupid. If you think I wrote the first, re-read and you will see that I am simply saying that men and women face different incentives which means that they will have different ability distributions in groups in which they self-select. I also am using the term “mental ability” as a shortcut for a very complex set of skills which basically make you successful in white collar jobs but are of limited use in blue collar jobs.