Maybe I’m just missing something, but isn’t the most likely explanation for the apparent link between hiring Yale Law clerks and getting questioned or reversed that the trial judges who don’t care much about getting reversed also are unusually likely to hire Yale Law clerks?
This is anecdotal, but my sense is that a pretty specific group of trial judges regularly hires Yalies, and that these judges are unusually likely to see themselves as pathbreaking judges who chafe against what the appellate courts tell them to do. If their politics line up correctly, Yale students will often see these judges as heroes of the law and want to clerk for them in part because they “push the limits of the law” (a.k.a. make stuff up that seems cool) in ways that often lead to reversal.
If I’m right about that, hiring Yale clerks will be a consequence of being reversal-prone rather than a cause of it. That doesn’t mean that Yale graduates will be as good at identifying and following the law as graduates of other schools. But I’m not sure this paper sheds light on that question given the likely direction of causation.