I don't think it's economics at all!
I am an instructor at a university teaching high-level computer certification. Almost all my students work in industry, often making a very good wage. Some of my students are black, and they do better than most whites in the job market. Why? Because employers absolutely LOVE to hire them. It shows that those employers are diverse and non-racist. So all things considered, if the white and black enigneer are the same in all their certifications and experiences, the black person wins the job. The same goes for females. A black, hispanic female engineer with experience and certs--Heaven, to the Human Resources dept!
Now, this doesn't mean that a bunch of whites aren't being employed. There are way too few blacks going through all the hard work and study to be a successful network engineer. So most of these jobs go to whites, or I should say, most of these jobs go to the engineers from the largest demographic group, white males, who seem to be attracted the most to these type jobs. Call us nerds if you will, but there you have it.
Why do they vote, often AGAINST their economic interests?
Because the dems have been successful at telling them what they want to hear: The MAN is keeping you down.
Lately the've been able to modify this to the Republican Man is keeping you down.
Final note: Far more blacks I know are racists (hate or dislike whites and hispanics) than whites, who mostly walk on eggshells to avoid saying anything that will get them fired.
This is the best explantion, I have ever read.