Empirical studies find a strong positive relationship between a country’s per-capita income and price level of final tradable goods. Among alternative explanations of this observation, I focus on variable mark-ups by firms. Mark-ups that vary with destinations ’ incomes are evident from a clothing manufacturer’s online catalogue featuring unit prices of identical goods sold in 28 countries. Such price discrimination on the basis of income suggests that firms exploit lower price elasticity of demand for identical goods in richer countries. In order to capture that, I introduce non-homothetic preferences in a model of trade with product differentiation and heterogeneity in firm productivity. The model helps bring theory and data closer along a key dimension: it generates positively related prices and incomes, while preserving desirable features of firm behavior and trade flows of existing frameworks. Quantitatively, the model suggests that variable mark-ups can account for at least a half of the observed positive relationship between prices of tradables and income across a large sample of countries.

The Ramsey approach to policy analysis finds the best competitive equilibrium given a set of available instruments but is silent about unique implementation, namely, designing policies so that the associated competitive equilibrium is unique. This silence is particularly problematic in monetary policy environments, where many ways of specifying policy lead to indeterminacy. We show that sophisticated policies, whichdependonthehistoryofprivateactionsandcandiffer on and off the equilibrium path, can uniquely implement any desired competitive equilibrium. A large literature has argued that monetary policy should adhere to the Taylor principle to eliminate indeterminacy. We show that adherence to the Taylor principle on these grounds is unnecessary for either determinacy or efficiency. We also show that sophisticated policies are robust to imperfect information. Atkeson, Chari, and Kehoe thank the National Science Foundation for financial support and Kathleen Rolfe for excellent editorial assistance. The views expressed herein are those of the authors and not necessarily those of the Federal Reserve Bank of Minneapolis or the Federal Reserve System. The now-classic Ramsey (1927) approach to policy analysis under commitment specifies the set of instruments available to policymakers and finds the competitive equilibrium outcomes that maximize social welfare with those available instruments. The Ramsey approach