not contain any mathematical term, however, some footnotes added in the sixth edition in order to interpret Verri's economic thought into mathematical terms. The aim of political economy to increase national power, strength and happiness is achievable through an increased population, incentives to labor, increased production and an appropriate balance between it and consumption. Success in achieving this policy objective can be measured by at least three different means in the absence of reliable national output data, as Verri indicates at various points in his treatise. These are the balance of trade, which he regarded as an imperfect measure; the level of the rate of interest, which he saw as a better measure, and population size and characteristics, which he saw as the best measure because it could be most accurately measured. Verri's economic theory concentrates on three subjects: 1. prices; 2. aggregate equilibrium; 3. distribution. Theory of prices According to Verri, the price of a commodity is directly related to "need" and inversely to plenty. By "need", Verri does not mean any indeterminate desire, but the effective demand of goods, i.e. the level of demand at which the expected utility of any good is higher than the cost individual are ready to pay in order to acquire it . Verri stresses consumer sovereignty, by arguing that demand regulates supply and not the contrary. As to plenty, it basically depends on the market form: it is larger when the market approximates to perfect competition. An equilibrium between production and consumption The problem of equilibrium between production ("reproduction" in Verri's terms) and consumption is analyzed examining two opposed cases of disequilibrium. Verri's contribution is strictly connected here to the basic theoretical assumptions of his theory of action. It is also very original in its issues. The first case takes place when national consumption is greater than production and the balance of commerce is unfavorable. Unlike Hume, Verri pays no attention to deflux of money and to the ensuing deflation. His interest is devoted to real re-equilibrating mechanisms. There are two possible solutions to disequilibrium: the first one is negative and consists of factor mobility (emigration of a part of the laboring force). When the other solution prevails, new productive branches are created in the country: these new industries compete in quality and price with those located abroad, toward which the demand for imported goods was addressed. This process of import substitution