Sorry, I don't have access to a study directly on degrees. If you want that, go hire some social science people to study it.
However my personal, anecdotal experience is that peer coworkers that I've had who did not have college degrees have, on average, been better than ones who did. By "peer coworker" I mean "working with me, with a job title similar to or better than mine". By "better" I mean "impressed me more". My measure of being impressed is what I thought of the quality and quantity of work that I saw them doing.
I have no idea what their salaries were like. There were some that I know were making less than coworkers with degrees, even though I thought that their work was better. Most I never had a discussion about salaries with.
That said, on the whole I would wager that discriminated against workers get a worse salary even if their productivity is equivalent or better. Why? Because salary is the result of a negotiation, one of whose inputs is what your alternate options are. People are not paid what they are worth to the company. They are paid what the company thinks it needs to pay them to keep them happy, and the difference between that and their worth is kept by the company as profit. (Companies that do not act this way soon find that they are not able to make a profit and some time later find themselves out of business...) If some employees have a hard time being paid more elsewhere, then they will often be satisfied with less from you.
This phenomena is presumably why the paper that I pointed you to measured productivity on the basis of company growth and profitability, and not on paid salary.
However my personal, anecdotal experience is that peer coworkers that I've had who did not have college degrees have, on average, been better than ones who did. By "peer coworker" I mean "working with me, with a job title similar to or better than mine". By "better" I mean "impressed me more". My measure of being impressed is what I thought of the quality and quantity of work that I saw them doing.
I have no idea what their salaries were like. There were some that I know were making less than coworkers with degrees, even though I thought that their work was better. Most I never had a discussion about salaries with.
That said, on the whole I would wager that discriminated against workers get a worse salary even if their productivity is equivalent or better. Why? Because salary is the result of a negotiation, one of whose inputs is what your alternate options are. People are not paid what they are worth to the company. They are paid what the company thinks it needs to pay them to keep them happy, and the difference between that and their worth is kept by the company as profit. (Companies that do not act this way soon find that they are not able to make a profit and some time later find themselves out of business...) If some employees have a hard time being paid more elsewhere, then they will often be satisfied with less from you.
This phenomena is presumably why the paper that I pointed you to measured productivity on the basis of company growth and profitability, and not on paid salary.