A direct result of capitalistic forces! When women entered the workforce en masse in the late 20th century, wages began to fall, almost in lockstep, as corporations realized they could pay workers less. Because with more workers on the "market," somebody would eventually accept a position for less pay.
Collective bargaining offset some of that pressure, but conservative forces, some of them led by Ronald Reagan, managed to eviscerate US labor law.
It's sad how many working-class people support the Republican Party despite that, voting against their own economic interests.
I guess the Party is clever, or something. Consider the fact that many anti-labor laws are called "right to work" laws by Republicans. As in, the right to work for much less pay and no union champion to fight for you.
Sigh.