Inflation and the Informativeness of Prices
研究通货膨胀导致的相对价格变动如何损害消费者福利。通过一个消费者与厂商建立长期关系的模型，发现通胀降低当前价格对未来价格的信号作用，导致消费者决策失误并增加厂商加价，在中等通胀率下影响显著。
Inflation and the Informativeness of Prices Laurence Ball (bio) and David Romer (bio) Abstract This paper studies the welfare effects of the relative-price variability arising from inflation. If customers and suppliers form long-term relationships, prices have an informational role: a potential customer uses current prices as signals of future prices. Inflation reduces the informativeness of current prices, causing customers to make costly mistakes about which relationships to enter. In addition, the reduced informativeness of prices makes demand less price elastic, thereby increasing markups. Both effects can be quantitatively significant at moderate inflation rates. Although inflation is widely viewed as a major economic problem, economists have yet to give a clear account of why it is costly. An appealing but vague theme in many discussions is that inflation reduces the efficiency of the price system. Relative prices are the tools with which the invisible hand guides the economy to efficient allocations. When inflation occurs, prices do not rise in tandem; instead, different nominal prices adjust at different times. Thus, relative prices deviate from the levels dictated by fundamentals. As Fischer (1981) puts it, "inflation is associated with relative-price variability that is unrelated to relative scarcities and hence leads to misallocations of resources." This paper asks whether this idea can explain important welfare losses from inflation. The relative-price variability arising from inflation potentially harms both the suppliers who set prices and sell goods and the customers who purchase the goods. It is not plausible, however, that the losses to price setters are large. Price setters have a simple means of stabilizing relative prices: they can adjust nominal prices frequently to keep up with inflation. Since the costs of such price adjustment often appear small, the amount of relative-price variability that suppliers permit must not impose large costs on them. Any major costs of price variability must fall on consumers. [End Page 177] In conventional economic models, however, relative-price variability does not harm consumers. If markets are Walrasian, price variability raises consumer welfare because indirect utility functions are quasi convex in prices (Waugh 1944). Price variability benefits consumers because it creates opportunities for substitution toward low-price goods. A similar result holds for markets in which consumers search across sellers; in this case, price variability benefits consumers by raising the returns to search (Kohn and Shavell 1974). These microeconomic principles help explain economists' difficulties in formalizing the idea that inflation is harmful. This paper presents a model in which inflation-induced price variability reduces consumer welfare. The crucial feature of the model is that prices have a role beyond their allocational role in Walrasian markets. In our model, prices also have an informational role. Specifically, we consider consumers who enter long-term relationships with sellers. In deciding whether to enter a relationship, potential customers use a firm's current price as a signal of the prices it will charge in the future. When inflation causes relative prices to vary, it reduces the information about future prices in current prices. We find that this loss of information harms consumers substantially. The remainder of the paper consists of five sections. Section 1 presents our basic model. Firms sell a good to consumers who participate in the market for two periods. Firms differ in their costs of production, and consumers differ in their tastes for the good. The aggregate price level rises steadily, and firms adjust nominal prices every two periods; thus, a firm's relative price alternates between a higher level when it adjusts and a lower level when it does not. When a consumer enters the market, he meets a firm, observes its current price, and chooses whether to buy the good. There is a fixed cost of establishing a customer relationship with a seller. This assumption leads to long-term relationships; in equilibrium, a consumer buys either in both periods of life or in neither, despite the fluctuations in prices. Section 2 derives the equilibrium of the model, and Section 3 determines the welfare effects of inflation. When a consumer decides whether to buy from a firm, he uses the firm's initial price to estimate its average price over the two periods he will be in...