In the Colorado Community College System, 78 percent of instructors are employed part-time Rocky Mountain PBS I-News reports. Their pay is lower than full-time professors, and they're often without benefits, sick leave or job security, even though they teach the same work loads: 

For “part-time” and “full-time” instructors teaching identical standard credit loads of 30 hours per week, the system estimated it would spend $20,828 on average this year in salaries for adjuncts and $53,693 on average for full-time instructors, who also receive benefits, according to budget documents.

The difference in pay means that part-time professor Nathanial Bork scrapes by, unable to pay to diagnose his daughter's developmental disability. But the difference in pay doesn't mean that he's not an effective teacher:

“He was the first professor who treated me as a person,” said Christina Mazingo, who flunked out of her first try at college. Mazingo now supports herself as a nanny as she works towards nursing school.

Gene Gonzalez is a former Marine who says he suffers from post-traumatic stress disorder and a traumatic brain injury. “There are times I am so fatigued while I come to his class,” Gonzalez said. “But once his lecture starts, I feed on his motivation and energy.”