Your education level has nothing at all to do with allot of people earning potential. I was making more than my friends who had masters in the early 90's before I even finished my associates. I know constructions workers with no more than a HS diploma or less who own companies or make at least 6 figures. It boils down to what you do with what you have, not just what you have.
The poll in my opinion should be divided by income...
0 - 20,000 Poor/below poverty level
21,000 - 35,000 Working
36,000 - 50,000 Traditional Middle
51,000 - 65,000 Middle
66,000 - 100,000 Upper Middle
101,000+ Upper Middle+
I am talking single person income, not couples etc.