The paper examines the behaviour of the yield curve of the knowledge considered as production factor. The concepts of complementarity and substitutability among classical production factors are revisited in order to put the bases to analyse the special production factor (a species of the neo-production factors) namely knowledge. In this context, some distinctions are made between information and knowledge putting in view the added value of knowledge related to information. Some graphical construction and algebraic formalisms are convoked in order to better ground the final conclusions regarding the increasing nature of the knowledge yield curve in the knowledge-based society. The approach is preponderantly logic and conceptualized, trying to get general results which could then be tested, by other researchers, in order either to corroborate or to reject them.