AbstractFixed factors in the international grain‐marketing system reduce flexibility and make adjustment to variable trade volumes difficult. A theoretical model is used to show how this causes marketing costs with trade instability to exceed those occurring under stability. Also, it is demonstrated that the marketing system increases the adverse effects of price variation on importers and exporters. Supporting empirical evidence, primarily dealing with ocean shipping, is presented. The results suggest that stable trade volumes may reduce marketing costs significantly. Thus, the marketing system should be considered in questions dealing with instability in the international grain trade.