An accurate kind of book-keeping which keeps these three elements of income separate is more generally practicable as civilization advances. We might call it the _economic balance_. Where commerce is very thriving it is even customary to provide by law that those classes who need it especially should have this species of book-keeping. People in a lower stage of cultivation, with their poetical nature, are unfriendly to such calculations.[145-4] [145-5] And where natural-economy (_Naturalwirthschaft_) or barter prevails, a book-keeping of this kind of any accuracy is scarcely practicable. The ratio which net income bears to gross income is a very important element to enable us to judge of the advantageousness of any method of production. If every producer should succeed in consequence of keeping his books in this manner, in determining exactly the cost to him of each of his products, this would be an economic progress similar to that of general spread of good chemical knowledge in the arts. On the amount of _free_ income, on the other hand, depends all the higher enjoyment of life, all rational beneficence, and the progressive enrichment of mankind.[145-6] [Footnote 145-1: Similarly in _Sismondi_, N. P., II, 330, and _Rau_, Lehrbuch, I, § 71, a.] [Footnote 145-2: Called by _Hermann_, loc. cit., simply income.] [Footnote 145-3: This truth _J. B. Say_ has exaggerated to the extent of claiming that gross and net income are one and the same so far as entire nations are concerned. (Traité, II, ch. 5; Cours pratique, III, 14; IV, 74.) But the gross profit of the entire production of any one year is much greater than the simultaneous net income of all the individuals engaged in it. This is accounted for by the fact that in such production an amount of circulating capital is invested which was saved from the net profit of previous economic times. Compare _Storch_, Nationaleinkommen, 90 ff. _Kermann_, loc. cit., 323 ff.]