From a purely business view, any kind of pay gap based on unimportant factors such as race and gender should be completely illogical. Just the idea of needing quotas for certain groups of people will certainly reduce productivity.
If I'm running a company, one of (if not) the highest priorities is obviously profit. If I had the option of hiring two people of equal qualifications and one of them is willing to work for less, I'm obviously going to hire the person that's willing to work for less.
Yes, it can be considered exploitation, but that's just business. If the business is offering and the people are willing, it's a fair transaction.
Thus, the majority of any workforce should theoretically end up being the group of people that are on the worse side of the pay gap.
It's also presents many great publicity options if your company mainly staffs the unappreciated workforce.