Job heterogeneity doesn't distinguish these situations nearly that much. The relevant comparison between academia and McDonald's is probably between regular emp

Job heterogeneity doesn't distinguish these situations nearly that much. The relevant comparison between academia and McDonald's is probably between regular employee and store manager/PhD Student and professor. In both cases promotion to the next level is plausible and happens regularly. If we consider non-lawyers employed by a law firm, then we should do the same with a university, which would distinguish both from the drug gang/McDonald's type where the bottom run has more promotion opportunity. Of course, this isn't even really right about academia -- a large university employs lots of people at many levels and it's perfectly possible to be promoted from administrative assistant to a management role. It is true that some professions, such as university faculty, law, and medicine, have specific credential requirements that limit advancement into those professions from other parts of the organizations that employ such professionals. But this is a way that academia etc is _different from_ a drug gang, not similar to it.