From Georgetown University's Center on Education and the Workforce. The authors describe the paper this way:
A four-year degree is the surest path to a middle class job, but what about jobs for workers in the middle? In a new report, we find that there are 29 million jobs that pay middle-class wages and don't require a four-year degree. We also explore in major detail the five essential Career and Technical Education pathways that lead to these jobs: employer-based training, industry-based certifications, apprenticeships, postsecondary certificates, and associate's degrees.