James Buchanan … produced several seminal contributions to the literature prior to the appearance of The Calculus, and a continual stream of books and articles afterward. I view Buchanan's Nobel Prize as a reward for this great body of work, and not just limited to The Calculus. Pursuing this line of reasoning, Gordon Tullock's prodigious research output following the publication of The Calculus also justifies a Nobel Prize. Indeed, Tullock's (1967c) seminal analysis of rent seeking, and his subsequent work on this topic might be regarded as sufficient achievements for the awarding of a prize.

James Buchanan, Gordon Tullock, and The Calculus (2012)