Abstract: | When a set of industries is kept in long‐run equilibrium, it is never possible to change just one price at a time. But when various (or all) prices are changing, the direction of change of any one price can depend on the numéraire adopted. What does it mean, then, to say that a long‐run supply curve is upward (or downward) sloping? Can this qualitative property be independent of the numéraire in terms of which the product price is being measured? In general, it cannot. |