Extra Surplus-value: The Missing Link of Marx's Transformation Theory

It has been lasting for a hundred years for the debate on the value transformation problem. A undeclared proposition of the debate is that Marx has one model of value transformation,but actually Marx has two: the model without capital flow and the theory emphasizing capital flow. The essence of the transformation problem is to explain the historical evolution of the value law from simple commodity economy to capitalism economy,of which the motivation is the progress of productivity and cross-sphere flow of capital. Therefore, the only approach to solve the transformation problem is to make the progress of productivity and cross-sphere flow of capital as the basic proposition. In the historical process of the progress of productivity, extra surplus-value is the core concept.