Trade uncertainty and the two-step procedure: The choice of numeraire and exact indexation

Summary In a small open economy it is optimal to first maximize national income and second choose the best consumption point.The same two-step procedure under (quantitative) uncertainty is suboptimal if one of the goods is used as numéraire. Optimality is restored however, if nominal prices are deflated by the exact price index. Hence there is equivalence between the appropriate two-step procedure and the introduction of a stock market under uncertainty (Diamond 1967) under ideal circumstances.I would like to thank, without implicating, Peter van Bergeijk, Steven Brakman, Willem Buiter, Richard Gigengack, Jean-Marie, Viaene, Casper de Vries and an anonymous referee for useful comments and Angelique van Haasteren and Martijn Herrmann for graphical assistance.