TL;DR - The wage gap will simply never close, for a few reasons that I am about to explain.

FIRST OF ALL

When I'm discussing the wage gap, I'm talking about the fact that women who work full time generally make 77 cents for every dollar a man makes working full time. This statistic does not account for different life choices, different hours worked, and different industries that men and women typically work in. I am not discussing the gender pay gap for the same work in which women are estimated as making anywhere from 90% to 98% of what men make for the same work. Now that we've clarified that, we can move on to the reasons that the gender wage gap will never ever close.

Reason #1: Incentives

Men have a greater incentive than women to excel in a career. This incentive is success in mate selection. Women look for a man with a good career, wealth, and prestige. These qualities are not nearly as important for a woman to have when trying to find a man. Men care much less about these things in a woman. Therefore, men are forced to place a much greater emphasis on their career than women. We quite literally have no choice if we wish to be successful in the dating game. An ugly man can marry a 10/10 trophy wife if he's a mulit-millionare CEO or a rapper or an athlete. An ugly woman cannot redeem her dating outlook with any amount of career success. Sorry ladies, its just not fair.

Reason #2: Interests

Studies like the ones in this documentary, which is found on the sidebar, have shown that baby boys spend more time looking at inanimate objects like nuts and bolts than baby girls do, while baby girls spend more time looking at faces than baby boys do. Testosterone literally makes our brains different than female brains. We are generally less empathetic, less social, and more interested in the way systems work. Hence, the fields of engineering and computing are dominated by men. And the fields of child development and elementary teaching are dominated by women. There are many feminists who yell that more girls should go into STEM: why don't these feminists themselves just go into STEM? Because they're simply not interested, in general. Disclaimer: I'm not insisting that women can't succeed in STEM, I have had girlfriends that are succeeding in engineering and can kick my ass at math. I'm saying that women in general are not as interested in these things as men in general. So put down your pitchforks.

Reason #3: Feminism and Victim Culture

If you are a woman, you can base your entire identity around the fact that you are a feminist. In fact you can make an entire career out of being a feminist. There are degrees in feminism, and degrees in Women's Studies