Diminishing Returns is a concept deeply rooted in economic thought. After being introduced by Turgot in 1767 it has become accepted as one of the cornerstones of contemporary economic theory. My interest in this area started in the fall semester of 1971 at U.C. Berkeley where I was enrolled in Professor Ronald W. Shephard's class on the theory of production. Shephard introduced me to his work on the Law of Diminishing Returns, and encouraged me to continue that work. This monograph is a result of my inspiring experience with Professor Shephard; and I am sincerely grateful to him for...