I don't pay much attention to the minority gap, so I have very little opinion there. I assume it is similar to my women/men gap discussion below.
Yes in some fields there is a wage gap. But in many fields there isn't. A minimum wage job at McDonald's is a minimum wage job whether you are male or female. A government job is the same wage whether you are male or female. There are a lot of fields where the salary is fixed and thus there are no differences.
In other areas, the difference can easilly be explained away. Number of hours worked is the biggest factor. In many jobs, men on average make say 20% more per year than women in the same job. Sounds unfair doesn't it? Not when you look further. In most of those situations, men work on average about 20% more per year than women in the same job. It balances out - per hour worked the wage is about the same.
In cases not covered by those above, women sometimes do have a wage gap. Then you have to look at other details. In our society, women tend to have more of a support job (the husband tends to be the biggest earner). Suppose the husband is an engineer making $70k a year and the wife is a teacher making $35k a year. It makes little sense for a wife to find a better paying job in another city that makes $40k a year if that means the husband may have to settle for a job making $60k a year when he moves to another city. In most cases, it is best for the higher earner to pick the city and the second earner (most often the female) to take what is available. Thus women just settle for a lower paying job so that their family is overall better off.
Other times women just don't ask for raises or don't demand a good wage when hired, they aren't aggressive enough in this area.
Other times, women just don't have the experience. Sorry but there are few women who have 35 years experience running a major corporation. Women didn't go to college in mass back then and they didn't get the management jobs back then. So you are comparing a man with 35 years experience managing a corporation to a woman with 20 years experience managing a small business. Yes the work is the same but the qualifications aren't. This is improving, especially now that women outnumber men in colleges. But it takes time.
What is left is very few fields where there is a REAL difference in wages. I think this difference is discrimination and needs to be addressed. But for the most part, these are rare cases in isolated industries.
Let me go get data, I think I have some that is relavant.