Since the 1970s, several major schools of Marxian economics have arisen in response to the transformation problem–related challenges of the neoclassical and Sraffian schools. Analytical Marxists held that the transformation problem disproved the labour theory of value and based their Marxian social theory on a combination of the Fundamental Marxian theorem, game theory, and other neoclassical and mathematical tools. Empirical Marxists, including Anwar Shaikh, Moshe Machover, and Paul Cockshott, maintain that since empirical data bears out the correspondence of prices and labour values, the transformation problem is irrelevant. Followers of the temporal single system interpretation and the new interpretation argue that critics have misunderstood Marx's definition of value and that, correctly defined, there is no difference between value and price.