The large aggregates in the economy – consumption, investment, production of the domestic and the international sectors, international capital flows, financial accumulation and indebtedness – are analysed in this book as problems in time-optimisation for enterprises and households. The effects of fiscal and monetary policies along with exchange-rate variation are examined, and their simultaneous use for stabilizing demand are found to be necessary. All household decisions on consumptions, savings, and financial disposition are conditioned by uncertainty, and similarly for firms, who make more complex simultaneous decisions on production, real investment, financing, and market strategy. The marginal efficiency-of-investment function derived from these decisions is fundamentally different from the marginal productivity of capital in the neoclassical sense. An economy which grows through the accumulation of capital, increase in labor supply, and technological progress is the framework in which all of these variables move. This codetermines the allocation of factors between domestic and international production, and the development of foreign trade. The growth both of the public debt and of international investment are treated in depth.