I do not know for certain if there is a wage gap between male and female employees working the same jobs. It seems absurd that a boss would allow a 30% difference in income between the men and women under their employ. Were such employees to compare their salaries, the resulting tension would be tremendous.
And yet, salaried employees do not typically compare their incomes, so it is possible that the problem does exist...but how widespread is it? Does it exist everywhere? Until people are more willing to say what their exact salaries are, data on the issue will be defficient.
On the other hand, there is a clear difference in pay between the professions dominated by men and those dominated by women. This is usually explained as the male-led industries being more dangerous and/or more difficult -- yet nursing is also difficult and dangerous; teaching requires great skill and talent; social workers have a thankless job keeping the poor and the broken and the lost from complete despair. Why, then, are these positions not typically paid well, for being both difficult and valuable?
Lately I have heard that it is because these professions are dominated by women. That the association with femininity itself causes these jobs to be paid poorly. The most frequent example given is surgical work in Russia: whereas American surgeons tend to be men, Russian surgeons tend to be women. And so the position is there considered feminine, less prestigious. What is considered a "Pink collar job" shifts -- wherever women go, the prestige of a profession drops.
Wages seem to be based not on objective value, but on what a culture deems prestigious. (What a shocker, right?) Those jobs that are considered more prestigious, like banker or CEO or surgeon or baseball player, get paid more. The less prestige a job has, the less it gets paid, until you hit bottom at prison slave labor, where the salary varies between cents per hour and nothing at all.
I will give you an example from my own life. I intend to become an archival technician for the US government, somewhere, in some capacity. The salary for the position varies between $35,000 and $50,000 depending on which agency is involved. I was taken aback when I learned of this, because I thought the position deserved a lower salary. I had been doing the same work at my school for $500 per month plus waived out-of-state tuition fees...which I suppose was where most of the monetary value in that position went. But still, $50,000 for an archival technician post?
I have no idea what such a post deserves. I have no idea how anyone would put a monetary value on archival work. By its nature, the labor only bears fruit years or even decades later -- it's not a position or industry that directly generates more than a pittance of currency.
Which means that the salary isn't based on an objective measure, but on what someone, somewhere, thinks the position deserves.
There's the key -- wages are decided based on human judgment. They vary by place and by era because people decide one position is more or less worthy than another. Across places and eras, the judgments seem to be decided on the basis of prestige, masculinity versus femininity, and the lowest price the boss thinks they can get away with. Mostly the latter, really. Bosses don't like to pay more for piecework and physical labor than they absolutely have to. Sometimes that means you get paid chickenfeed. Sometimes you get a boss who is magnanimous. In my case, the post of archival technician for the federal government is paid well because the government doesn't have the same pressure to reduce salaries that private business does.
The salary of an archival technician depends upon the prestige and generosity of the institution it is attached to; there are plenty of archival jobs in the country that pay quite poorly. Such as being the director of the community archives at the Urbana Free Library. The director has to teach classes at the university in order to pay the bills.
Currently we are in an era in which wages and salaries are largely decided by prestige, and by individual negotiating skills. There is another factor lately overlooked: Unions. I say lately overlooked befuse when American buinesses realized they could jump ship and put their factories in Asia, it severly reduced the influence of labor unions. The era of America that Donald Trump thinks was "great" was mostly an era in which workers in heavy industries were able to effectively negotiate the price of ther own labor. That's fallen by the wayside.
We're in an era where salaries and wages are accepted, endured, survived, not one in which they are negotiated to make life bearable.
Therefore, when I hear someone saying that poor people ought to work harder to earn more money, I remind myself that, while most people OUGHT to have an effective say in the price of their labor, they do not. Only the self-employed are able to set the price of their labor. And even they face dispute, when their customers demand a lower price.
For those working under a boss, the company or institution above them plays the part of the customer demanding a lower price. Directors of companies face a lot of pressure from their boards of shareholders to save money by any means necessary. Boards of directors direct the company to reduce wages to the lowest possible market price, which is low indeed when companies are able to pay workers outside this country lower wages than they do here. And any worker who wants to unionize gets quietly dismissed.
And at the other end of the chain, you, the customer in the store, demand everyday low, low prices for your goods. Between store customers and company directors, individual service workers have nobody behind them to back up their own needs.
There is no true, objective price of labor. There is only what we decide. If people decide that a profession is less prestigioius because it's mostly represented by women these days, the salaries of those jobs fall. If people decide that service work only deserves a pittance for the effort, the pay barely ever rises above minimum wage.
I get annoyed when I hear people talking about how wages are set by market forces and market forces alone. It feels so passive, to just LET social and economic forces decide how people should be paid. If there's any hard work that poor people can do to earn more money, it should be in the areas of unionizing service workers, of demanding that the perople doing the work have real power over what they are paid. It is hard work, because bosses are tight-fisted, and are far more willing to spend money on keeping wages down by any means necessary than upon increasing wages.
For all who believe that their demographic is poorly paid, be it women in pink-collar jobs or poor people working at three different fast-food places, what must be done is difficult and dangerous work: to make it more expensive for the boss to depress wages than to raise them.
If there is no other way to raise the price of labor than to raise hell, so be it.