Uncertainty and Tobin´s q in a monopolistic competition framework.

This paper combines the adjustment cost hypothesis of Tobin's q models with Malinvaud's proposition that demand uncertainty matters in explaining investment. Demand uncertainty allows for ex-post excess capacity and leads firms to look at the expeeted excess capacity in deciding about investment. Marginal q is shown to be smaller than average q, the difference being explained by the degree of capacity utilization (DUC).Tobin's q; Investment; Monopolistic Competition; Quantity Rationing Model;