Let's address your initial concern about the pay gap by gender.  Payscale (a compensation mgmt. company) recently produced a study that showed the median salary between men and women among all jobs has women making 82 cents for every dollar men make.  This is 18% difference is the raw gender pay gap.  When looking at the same job with same years of experience and education/skills the gap narrows to 2%.  This 2% is called the controlled gender gap. Payscale's study draws no conclusion for the reason for this 2% gap but some form of bias would be the obvious.  The study shows that the controlled gender gap has been closing by 1% point every 4-5 years with the expectation of it closing to near zero by the end of this decade.

Now, to your concern about the pay gap by race.  Payscale also studied wage disparity among men of different races. The median income for a black male was 87 cents for every dollar earned by a white male.  This would be the raw race pay gap cutting across all jobs, industries, etc.  The controlled race gap was the same 2% shown for women.  The controlled race gap too has been closing over the past two decades albeit slowly.

Hope this helps.