Perhaps the most surprising element of this is that, unlike most professions in the world, Hollywood did not start out with the kind of consistently divided financial gender lines that it's currently tolerating. It's true that in 1937, Fred Astaire made $211,666 to Ginger Rogers' $124,770, but consider the fact that, that same year, the top two highest earners were Gary Cooper ($370,214) with Mae West close behind ($323,333). Five years prior, in 1932, the top three earners were actresses. So it would seem that opportunities to get into the same earnings ballpark as men were more viable for actresses 80 years ago than they are today -- which is pretty insane if you think about it. Scarlett Johansson may have earned the same as Chris Evans and Chris Hemsworth for The Avengers, but it was an unusual enough situation to warrant press attention.

So how did we get here? It's easy to track where the shift in Hollywood earnings began, thanks to the Top Ten Money Making Stars Poll -- a unisex list. The results of the very first poll came out in 1932, and not only revealed that the top three earners were female (Marie Dressler, Janet Gaynor and Joan Crawford), but that the list was 50/50 men and women. That trend continued through the 1930s.

By 1942, however, the list was dominated by men, with just Betty Grable and Greer Larson scraping into the top ten in the No. 8 and 9 positions. Ten years later, the problem persisted. 1952's list contains only two women -- Doris Day at No. 7 and Susan Hayward at No. 9. By 1957, there wasn't one woman left on the top ten earner's list.

Some recovery came in the 1960s. Marlon Brando might have been the first actor to earn $1 million for a movie, for 1962's Mutiny on the Bounty, but it took Elizabeth Taylor less than nine months to catch up, with her salary on Cleopatra. The top ten money makers poll was dominated by men for the entire period, but it was women (Doris Day, Elizabeth Taylor and Julie Andrews) topping the list for all but two years that decade.

It was in the 1970s that a major shift happened. That was the decade that women were all but wiped off the highest earners' list, and frankly, women in Hollywood have never recovered. That shift, at that particular time -- the peak of second wave feminism -- is an ironic premonition of where we are now.

"Second Wave Feminism - 1960s-1970s" / YouTube

Arguments about the gender pay gap are frequently disrupted with suggestions that women are simply choosing lower-paid jobs, working less hours (because of their still-dominant role in caregiving responsibilities) or just not pushing hard enough. What the movie industry is effectively showing us is that none of those factors actually matter. Men and women in Hollywood are doing the same jobs (though meaty roles are harder to come by for women simply because they're not getting written / greenlit), they have the same agents, the same PR people and the same means to deal with child care as their male counterparts. The reason actresses are making less is very simple: the film industry has a very obvious, very systemic sexism problem.

In the end, Hollywood is symbolic of what women face in almost every industry and profession in the United States -- and where you live in the country does make a difference. In 2015, women working in New York City made 89 cents for every male dollar, but in Wyoming that amount dropped to 64 cents. The gender pay gap also significantly increases for women of color.

Diane KeatonDiane Keaton

How Did We Get Here? Marky Mark and the History of Hollywood’s Gender Pay Gap