60 SOCIAL SCIENTIST Two stages in the process of innovation can be distinguished. In the first, only one (or a few) individual capitalist realizes the innovation, which results in extra profit for him. In the second stage., the innovation will be imitated by all producers in the branch so that the price of the product will decrease according to the decrease in the costs of production. In other words, the extra profit will disappear. According to Marx, this process of increasing the productivity of labour will increase the constant capital per labourer in physical terms. This leads, in spite of ^cheapening the elements of the constant capital" in the course of this process, to an increase in the organic composition of capital. Moszkowska assumes that there is an even development of technical progress in both Department I (producing means of production) and Department II (producing means of consumption), so that the elements of the constant capital are depreciated according to the increase in the productivity of labour. With her model she demonstrates5 that the higher the organic composition of capital the higher must be the progress of productivity required to ensure a given extra profit for the individual innovator. Thus, if the organic composition of capital is rising, the minimum rate of increase in the productivity of labour will also rise over time. But an increase in this rate means that the increase in the organic composition of capital and so the fall in the rate of profit is slowing down. If the increase in the productivity of labour exceeds the increase of the elements of constant capital in physical terms, the fall of the rate of profit will come to a halt. Prerequisites/or a Fall Thus, whether the fall in the rate of profit is only a transitional or a continuous, though decelerating, process, depends on the question whether the rate of increase in the productivity of labour will exceed the rate of physical extension of the elements of constant capital per labourer. It can be demonstrated that this depends on the degree of exploitation and the extent of extra profit required by the innovator.6 The higher the degree of exploitation and (or) the higher the extra profit, the higher will be the probability of the first rate exceeding the latter. So in the early stages of capitalism, when the organic composition of capital as well as the degree of exploitation are comparatively low and the forces of competition are strong (which means that the capitalists are forced to implement even minor innovations yielding only a low extra profit) the rate of profit will most probably fall. But the rate is likely to be constant in the stage of mature capitalism. There is one assumption in Moszkowska's model which could provide a possible basis for criticizing her approach. She assumes that there is an even development of the productivity of labour in both