This paper analyses some of the approaches that explain the variation in profits based on the concept of total factor productivity (TFP), using the framework of the neoclassical theory of production. In this field different explanatory decompositions of the variation in profits have been suggested. These are based on mathematical expressions that quantify different effects on the profit variations, such as the TFP and the price recovery. We will analyse alternative proposals for the decomposition of profit variations over time, using a common framework which draws on Solow's concept of technical change. We introduce the notionof "duality" among TFP measures which allows us to show that several decompositions of the profit variations suggested in the literature are in fact 'dual' to each other and therefore they measure the same thing. © 1992.