Monopoly Capital
One of the key contributions of "Monopoly Capital" is its application of the concept of economic surplus. The economic surplus is most simply the difference between “what a society produces and the costs of producing it. The size of the surplus is an index of productivity and wealth, of how much freedom a society has to accomplish whatever goals it may set for itself. The composition of the surplus shows how it uses that freedom: how much it invests in expanding its productive capacity, how much it consumes in various forms, how much it wastes and in what ways.”