The 'counterweight' which in the hand of the workers increases the 'value' of 'what is retained' by the entrepreneurs, can in this context only be the demand. Once again, we have landed happily at the familiar _Ort_ of v. Kirchmann's where workers and capitalists exchange their incomes for the surplus product, and where the crises arise because variable capital is small and the surplus value large. This peculiar notion has already been dealt with above. There are other occasions, however, when Rodbertus advances a somewhat different conception. The interpretation of his theory in the fourth _Letter on Social Problems_ is that the continual shifts in the relations of demand, evident in the share of the working class and caused by the share of the capitalist class, must result in a chronic disproportion between production and consumption. 'What if the entrepreneurs endeavour to keep always within the limits of those shares, yet the shares themselves are all the time on the decline for the great majority of the society, the workers, decreasing gradually, unnoticeably, but with relentless force?--What if the share of these classes is continually decreasing to the same extent as their productivity is increasing?'--'Is it not really the fact that the capitalists of necessity organise production in accordance with the present volume of shares in order to make wealth universal, and that yet they always produce over and above this volume (of previous shares), thereby perpetuating dissatisfaction which culminates in this stagnation of trade?'[258] On this showing, the explanation of crises should be as follows: the national product consists of a number of 'common goods', as v. Kirchmann puts it, for the workers, and of superior goods for the capitalists. The wages represent the quantity of the former, and aggregate surplus value that of the latter. If the capitalists organise their production on this footing, and if at the same time there is progressive productivity, a lack of proportion will immediately ensue. For the share of the workers to-day is no longer that of yesterday, but less. If the demand for 'common goods' had involved, say, six-sevenths of the national product yesterday, then to-day it involves only five-sevenths, and the entrepreneurs, having provided for six-sevenths of 'common goods', will find to their painful surprise that they over-produced by one-seventh. Now, wiser by this experience, they try to organise to-morrow's output of 'common goods' to a mere five-sevenths of the total value of the national product, but they have a new disappointment coming to them, since the share of the national product falling to wages to-morrow is bound to be only four-sevenths, and so on.