期刊名称：Discussion Papers in Economics / Manchester Metropolitan University
出版年度：2006
卷号：2006
出版社：Manchester Metropolitan University
摘要：In the absence of technological externalities, a rising supply price – that familiar and much loved ‘set piece’ in microeconomics textbooks – is usually explained by increasing marginal cost in identical competitive firms and by rising input prices, brought about by the expansion of the existing firms or by new entries1. The corresponding cost and supply curve diagrams are often found to have £ or $ costs/prices on the vertical axis or, even more often, they are supported by no indication of how costs/prices are being measured. Yet the firms’ choices can be expressed by functions which are known to be homogeneous of degree zero in input and output prices. A ‘money’ output price, as such, can never therefore matter: quite obviously, then, a ‘rising’ supply price must be defined relative to a real numéraire. The familiar diagrams are coherent with this central, homogeneity property of microeconomic theory only if ‘money’ is interpreted metaphorically, to mean any possible real numéraire: a ‘rising’ supply curve requires therefore that that ‘rising’ be numéraire-independent2. Only then can one safely omit any indication of the measurement unit of the output price or, which is the same, use the verbal convention of calling ‘money’ any arbitrary unit. But is this condition generally fulfilled? Does it never happen that an industry supply curve turns out to be rising or falling according to the mere, arbitrary choice of numéraire? It is surprising that such questions have received so little attention in the literature. To the best of our knowledge, the potential numéraire-dependence of a rising supply price was hinted at only by Joan Robinson in 1941. As she put it, “we cannot say whether or not the supply price (…) rises with an increase in its output until we know how prices are to be reckoned” (Robinson, 1953 [1941], pp. 236-37). Joan Robinson’s remark was insightful, but she confined herself to finding a numéraire in terms of which supply price is rising. It is the main purpose of this paper to show that the direction of change in the supply price can indeed be numéraire-dependent.
Loading...
