The analysis of external shocks of real nature, such as the oil shock, requires an intertemporal framework to properly investigate through saving and investment decision the outcome of the balance of trade. By now there are quite few works replying on such an approach, M. Obstfeld (1980), J. Sachs (1981, 1983), M. Bruno (1982), N. Marion (1984), N. Marion -L. Svensson (1984), yet they are far from explaining the large deficits of oil importing countries and the joint combination of trade deficits and fall in investment as the outcome of oil shocks. Even more surprisingly they disprove the intuition, which can be traced back to the income-expenditure model of a strict correlation between the magnitude of trade deficits and real income losses. M. Obstfeld's conclusion is that trade deficit, as consequence of the fall in saving, can occur only when there is a significant degree of substitution in the economy, when income losses tend to be at minimum. For J. Sachs (1981, 1983) real income losses per se do not lead to trade deficit, they matter for the balance of trade performance only in so far the oil shock is of temporary nature. The fall in investment due to permanent oil stock will tend to give rise to trade balance surpluses and the poor performance of the oil importers trade balance can be explained only by replying on the reduction in the world interest rate (J. Sachs 1981).