This paper examines the optimal debt contract between lenders and a sovereign borrower when the borrower is free to repudiate the debt and when his decision to invest or consume borrowed funds is unobservable. We show that recurrent debt crises are a necessary part of the incentive structure which supports the optimal pattern of lending.

In this paper, we build a model of the transition following large-scale economic reforms that predicts both a substantial drop in output and a prolonged pause in physical investment as the initial phase of the optimal transition following the reform. We model reform as a change in policy which induces agents to close existing enterprises using old technologies of production and to open up new enterprises adopting new technologies of production. The central idea of our paper is that it is costly to close old enterprises and open new enterprises because, in doing so, information capital built up about old enterprises is lost and time must pass before information capital about new enterprises can be acquired. Thus, an acceleration of the pace of industry evolution leads in the short run to a net loss of information capital, a drop in productivity, a recession, and a fall in physical investment. We calibrate our model of industry evolution, information capital, and transition to match micro data on industry evolution in the United States and macro data from the United States, Japan, and the former communist countries of Europe. We find that the loss of information capital that accompanies a major acceleration in the pace of industry evolution in an economy leads initially to a decade of recession and a five year pause in physical investment before the benefits of reform are realized.

The Ramsey approach to policy analysis finds the best competitive equilibrium given a set of available instruments. This approach 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 which depend on the history of private actions and which can differ 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. Our findings say that adherence to the Taylor principle on these grounds is unnecessary. Finally, we show that sophisticated policies are robust to imperfect information.

The key question asked by standard monetary models used for policy analysis is, How do changes in short-term interest rates affect the economy? All of the standard models imply that such changes in interest rates affect the economy by altering the conditional means of the macroeconomic aggregates and have no effect on the conditional variances of these aggregates. We argue that the data on exchange rates imply nearly the opposite: the observation that exchange rates are approximately random walks implies that fluctuations in interest rates are associated with nearly one-for-one changes in conditional variances and nearly no changes in conditional means. In this sense, standard monetary models capture essentially none of what is going on in the data. We thus argue that almost everything we say about monetary policy using these models is wrong.

Time-varying risk is the primary force driving nominal interest rate differentials on currency-denominated bonds. This finding is an immediate implication of the fact that exchange rates are roughly random walks. We show that a general equilibrium monetary model with an endogenous source of risk variation—a variable degree of asset market segmentation—can produce key features of actual interest rates and exchange rates. The endogenous segmentation arises from a fixed cost for agents to exchange money for assets. As inflation varies, the benefit of asset market participation varies, and that changes the fraction of agents participating. These effects lead the risk premium to vary systematically with the level of inflation. Our model produces variation in the risk premium even though the fundamental shocks have constant conditional variances.

How much discretion is it optimal to give the monetary authority in setting its policy? We analyze this mechanism design question in an economy with an agreed-upon social welfare function that depends on the randomly fluctuating state of the economy. The monetary authority has private information about that state. In the model, well-designed rules trade off society’s desire to give the monetary authority flexibility to react to its private information against society’s need to guard against the standard time inconsistency problem arising from the temptation to stimulate the economy with unexpected inflation. We find that the optimal degree of monetary policy discretion is decreasing in the severity of the time inconsistency problem. As this problem becomes sufficiently severe, the optimal degree of discretion is none at all. We also find that, despite the apparent complexity of this dynamic mechanism design problem, society can implement the optimal policy simply by legislating an inflation cap that specifies the highest allowable inflation rate.

A classic question in international economics is whether it is better to use the exchange rate or the money growth rate as the instrument of monetary policy. A common argument is that the exchange rate has a natural advantage since exchange rates provide signals of policymakers’ actions that are easier to monitor than those provided by money growth rates. We formalize this argument in a simple model in which the government chooses which instrument it will use to target inflation. In it, the exchange rate is more transparent than the money growth rate in that the exchange rate is easier for the public to monitor. We find that the greater transparency of the exchange rate regime makes it easier to provide the central bank with incentives to pursue good policies and hence gives this regime a natural advantage over the money regime.

During the Second Industrial Revolution, 1860–1900, many new technologies, including electricity, were invented. These inventions launched a transition to a new economy, a period of about 70 years of ongoing, rapid technical change. After this revolution began, however, several decades passed before measured productivity growth increased. This delay is paradoxical from the point of view of the standard growth model. Historians hypothesize that this delay was due to the slow diffusion of new technologies among manufacturing plants together with the ongoing learning in plants after the new technologies had been adopted. The slow diffusion is thought to be due to manufacturers’ reluctance to abandon their accumulated expertise with old technologies, which were embodied in the design of existing plants. Motivated by these hypotheses, we build a quantitative model of technology diffusion which we use to study this transition to a new economy. We show that it implies both slow diffusion and a delay in growth similar to that in the data.

This paper analyzes the effects of money injections on interest rates and exchange rates in a model in which agents must pay a Baumol-Tobin style fixed cost to exchange bonds and money. Asset markets are endogenously segmented because this fixed cost leads agents to trade bonds and money only infrequently. When the government injects money through an open market operation, only those agents that are currently trading absorb these injections. Through their impact on these agents’ consumption, these money injections affect real interest rates and real exchange rates. We show that the model generates the observed negative relation between expected inflation and real interest rates. With moderate amounts of segmentation, the model also generates other observed features of the data: persistent liquidity effects in interest rates and volatile and persistent exchange rates. A standard model with no fixed costs can produce none of these features.