And it's really, really annoying.
Okay it's more than annoying. It's discriminatory. There's this myth that keeps re-emerging when people discuss the discrepancy between mens' and womens' wages: That women are choosing fields with lower pay and thus get paid less. It's not true at all. Women and men in similar fields and positions, with comparable experience, don't make the same amount (via). According to this 2015 study "Women’s median earnings are lower than men’s in nearly all occupations, whether they work in occupations predominantly done by women, occupations predominantly done by men, or occupations with a more even mix of men and women." So it turns out women aren't choosing to get paid less (why would anyone choose that). But wait! There's more!
The pay rate declines when women enter a field.
So studying really hard and entering a high-paying field isn't actually going to help (un-fun fact, women spend more on their education and get less in return). "The gender gap in pay persists, not because women are less qualified or less ambitious, but because work done by women is valued less. Sometimes, that manifests itself in individual women being paid less than their male counterparts, and sometimes it looks like whole fields becoming less lucrative once women start entering en masse" (via). For men, the opposite is true: When men start entering a field the rate of pay goes up. Programming for example used to be a female-dominated field. When men started dominating the field the rate of pay increased.
This isn't a U.S.-centric problem either.
So moving probably won't help. In Russia for example doctors are held to similar standards that they are here. But it's one of the lowest-paid professions in the country (about $12,000 a year). And it's a field primarily dominated by women. Very different from what it's like in America (which might explain why becoming a doctor is such an attractive career path here despite the cost of medical school).
So, it's not just about having babies.
Actually, women's chances of getting hired decrease when they have children- men's chances improve. So women aren't actually opting out of jobs or working fewer hours (that difference persisted after factoring in hours worked, job type, and spouse's salary). Essentially, women are being forced out. Not only are they less likely to be hired when they become parents, but since they're getting paid at a lower rate than their colleagues they're more likely to run into problems finding affordable child-care. For some mothers, it's actually cheaper to stay home. So for women to come close to making as much as their male counterparts they need to be child-free, unmarried, and white.
Stuff like this matters.
The wage gap means women spend a longer time paying back student loans, it means that they're less able to be financially independent from their families and partners, and it means women need at least a Bachelor's degree to lift their families out of poverty (while men can get there with a high school degree). And frankly it's bad for our economy. If work can be under-valued for such arbitrary reasons, what kind of stability can we honestly expect?