sectors producing consumer goods and luxuries. In modern national accounts more subtle distinctions are made, for example between primary, secondary and tertiary production, semi-durable and durable goods, and so on. Role in political economy In his textbook The Theory of Capitalist Development (1942), American Marxist Paul Sweezy claimed: Marx explicitly rejected Sweezy and Uno's interpretation of use-value (see the previously cited quotation from 1859, in which use-value is distinguished from the general concept of utility). In a draft included in the Grundrisse manuscripts, which inspired the starting point of A Contribution to the Critique of Political Economy and Das Kapital, Marx states: In his text [http://maximumred.blogspot.com/2005/05/rosdolsky-on-marxs-use-value.html The Making of Marx's 'Capital'''], Roman Rosdolsky explains the role of use value in Marx's economics. Marx himself, in the introduction to his Grundrisse manuscript, had defined the economic sphere as the totality of production, circulation, distribution and consumption. However, as Marx did not live to finish Das Kapital, he did not theorise how commercial relations would reshape the sphere of personal consumption in accordance with the requirements of capital accumulation. Minor issues remained from these neoclassical theories, such as the question of the proper empirical definition of capital and labour in the laws of factor substitution. Other empirical issues include the so-called Solow Residual in which the heterogenous nature of labour is thoroughly explored for its qualitative elements beyond differentiation, and the concept of total factor productivity, prompting some to consider such things as technology, human capital, and stock of knowledge. Later scholars, such as Walter Benjamin, Fernand Braudel, Ben Fine, Manuel Castells and Michel Aglietta attempted to fill the gap in Marx's unfinished work. In modern times the theory has been extended to conclude that conversion of energy-driven work does not rely on labour-intensive inputs; thus use can be unsupervised work that develops a notion of human capital.Equation: A = P + hL(A, the Concept of Substitutive Work = P, the loss of Primary Productive Energy (which is P/Ep, the coefficient of efficiency) + h, the units of energy (which is the energy consumed by workers during work done) * L, Labour time per hour) Utility Marx's concept of use-value seems akin to, but in reality differs from the neoclassical concept of utility: Marx usually assumes in his analysis that products sold in the market have a use-value to the buyer, without attempting to quantify that use-value other than in product units