there's load of economists who write about how truly meritocratic companies would have no bias in them at all as that is the cheapest way to ensure that wage costs are kept as low as possible. However, the history of organized labour and pay disputes demonstrates that even the workers want to collude with management to keep certain groups (women, people of color) away from equal pay, so many disputes are settled by convoluted agreements which effectively discriminate and maintain the status quo.
I've lost the details of the books I read this in (and they were BIG books from the university library, so they. were. right.) as I didn't use that info in the paper I was researching at the time.
IT always drives me mad when threads come up about equal pay and people pile in saying 'that's ridiculous, no company would be so stupid to pay a man more if they can get a woman for less'. Not only are there huge numbers of statistics proving that women get paid less, but it's just a really wantonly blind attitude to discrimination and how it works.