A specular consequence of the same principle of effective demand is that investments (and, possibly, public expenditure) ‘generate’ the necessary savings to finance them. Once investments are determined and public expenditure is fixed, the principle of effective demand establishes the level of national income which originates the necessary and sufficient savings to be used to finance those levels of investments and of public expenditure. Some post-Keynesian economists, in particular Nicholas Kaldor, Joan Robinson and Richard F. Kahn, tried to find a way out of the impasse of the instability of an economic system’s equilibrium growth path. In such a special case, people can observe that prices reduce to a sum of quantities of labour: direct labour, indirect labour and hyper-indirect labour. A particular form of labour theory of value thus re-appears; it is a ‘vertically hyper-integrated’ labour theory of value, which differs from the labour theory of value considered so far, because it contains a new component: hyper-indirect labour.