The distinction between use value and exchange value is incoherent, so there is nothing to be gained by studying Marx's writings on it. Any theory of value that

The distinction between use value and exchange value is incoherent, so there is nothing to be gained by studying Marx's writings on it. Any theory of value that does not include the concept of marginal utility is a best worthless. There is certainly no consensus that the global rate of return is in long-term decline, and much evidence to the contrary, particularly over the recent decades when econometric data has become sufficient to measure it. And anyway, even if there were a secular trend, Marxian economics could not explain it because that theory is dependent on Marx's law of value, which is entirely contradicted by evidence.