That's the conclusion of a study by three colleagues of mine, Adam Chilton (just tenured, easy case!), Jonathan Masur, and Kyle Rozema (our Behavioral L&E Fellow).  I've not looked at the details of the study, but I wonder how much the results are affectedd by Harvard's historical pattern (changed in recent years) of hiring and then tenuring everyone based on good grades in law school, which results in more "dead wood" there than elsewhere.   Even if Harvard has some effect on the findings, I think their basic point is correct:  law schools, especially those maintaining a high scholarly profile, should be more demanding about tenure.