The production of consumer goods for I_v_ and II_v_ is not an end in itself, as it would be in a society where the economic system is shaped for the workers and the satisfaction of their wants. In a capitalist system, Department II does not produce means of consumption in large quantities simply to keep the workers of Departments I and II. Quite the contrary: a certain number of workers in Departments I and II can support themselves in every case because their labour power is useful under the obtaining conditions of supply and demand. This means that the starting point of capitalist production is not a given number of workers and their demands, but that these factors themselves are constantly fluctuating, 'dependent variables' of the capitalist expectations of profit. The question is therefore whether the natural increase of the working class also entails a growing effective demand over and above the variable capital. And that is quite impossible. The only source of money for the working class in our diagram is the variable capital which must therefore provide in advance for the natural increase of the workers. One way or the other: either the older generation must earn enough to keep their offspring--who cannot, then, count as additional consumers; or, failing that, the next generation, the young workers, must turn to work in order to obtain wages and means of subsistence for themselves--in which case the new working generation is already included in the number of workers employed. On this count, the process of accumulation in Marx's diagram cannot be explained by the natural increase of the population.