Carlo Zappia and I have been asking the same question of each other, and 
now turn to the list:  Daniel Ellsberg graduated from Harvard "under" 
John Chipman whom he "acknowledged" in his first academic article in the 
Economic Journal (1954, fn. 3). As for his Ph.D Thesis, the 2001 print 
(Garland Press) does provide information about who discussed parts of 
the thesis (Savage is acknowledged to have had a prominent role), but 
there is no mention of Chipman. However none of the people quoted is 
indicated as having been the supervisor, nor is there mention of any 
committee. My own reading of Samuelson's Harvard thesis shows no mention 
of a "supervisor", and no published source indicates any such person, or 
committee (although E. B. Wilson is thanked in several places). Which 
suggests the question:  was it Harvard's practice in the interwar and 
immediate postwar period to have Economics dissertations accepted 
collectively, with no formal committees, or supervisors? Any information 
would be appreciated.

E. Roy Weintraub