Research Database

Does the pattern of social connections between individuals matter for macroeconomic outcomes? If so, where do these differences come from and how large are their effects? Using network analysis tools, we explore how different social network structures affect technology diffusion and thereby a country's rate of growth. The correlation between high-diffusion networks and income is strongly positive. But when we use a model to isolate the effect of a change in social networks, the effect can be positive, negative, or zero. The reason is that networks diffuse ideas and disease. Low-diffusion networks have evolved in countries where disease is prevalent because limited connectivity protects residents from epidemics. But a low-diffusion network in a low-disease environment needlessly compromises the diffusion of good ideas. In general, social networks have evolved to fit their economic and epidemiological environment. Trying to change networks in one country to mimic those in a higher-income country may well be counterproductive.

We propose a simple method to help researchers develop quantitative models of economic fluctuations. The method rests on the insight that many models are equivalent to a prototype growth model with time-varying wedges which resemble productivity, labor and investment taxes, and government consumption. Wedges corresponding to these variables—efficiency, labor, investment, and government consumption wedges—are measured and then fed back into the model in order to assess the fraction of various fluctuations they account for. Applying this method to U.S. data for the Great Depression and the 1982 recession reveals that the efficiency and labor wedges together account for essentially all of the fluctuations; the investment wedge plays a decidedly tertiary role, and the government consumption wedge, none. Analyses of the entire postwar period and alternative model specifications support these results. Models with frictions manifested primarily as investment wedges are thus not promising for the study of business cycles. (See Additional Material for a response to Christiano and Davis (2006).)

No abstract available.

Intuitively, a patient trader should be able to make his trading partners compete to reveal whatever information is relevant to their transactions with him. This possibility is examined in the context of a model resembling that of Gale (1986). The main result is that, under assumptions having to do with asset structure and spanning, incentive-compatible elicitation of trading partners’ knowledge is feasible.

A classic result in the theory of implicit contract models with asymmetric information is that “underemployment” results if and only if leisure is an inferior good. We introduce household production into the standard implicit contract model and show that we can have underemployment at the same time that leisure is a normal good.

In this paper we develop a model in which a country faces a balance of payments crisis if constraints on its international borrowing bind. We use the model to describe the dynamics of the trade balance, capital account, and balance of payments of a country that borrows to finance consumption following sweeping macroeconomic and structural reforms and then hits constraints on its international borrowing. We compare the predictions of this theoretical example with events in Mexico from 1987 through 1995.

Our thesis is that poor countries are poor because they employ arrangements for which the equilibrium outcomes are characterized by inferior technologies being used, and being used inefficiently. In this paper, we analyze the consequences of one such arrangement. In each industry, the arrangement enables a coalition of factor suppliers to be the monopoly seller of its input services to all firms using a particular production process. We find that the inefficiencies associated with this monopoly arrangement can be large. Whereas other studies have found that inefficiencies induced by monopoly are at most a few percent of output, we find that eliminating this monopoly arrangement could well increase output by roughly a factor of 3 without any increase in inputs.

We examine entry across 113 national markets in 16 different industries using a comprehensive data set of French manufacturing firms. The data are unique in indicating how much each firm exports to each destination. Looking across all manufacturers: (1) Firms differ substantially in export participation, with most selling only at home; (2) The number of firms selling to multiple markets falls off with the number of destinations with an elasticity of –2.5; (3) Decomposing French exports to each destination into the size of the market and French share, variation in market share translates nearly completely into firm entry while about 60 percent of the variation in market size is reflected in firm entry. Looking within each of 16 industries we find little variation in these patterns. We propose that any successful model of trade and market structure must confront these facts.

The Pareto-like tail of the size distribution of firms can arise from random growth of productivity or stochastic accumulation of capital. If the shocks that give rise to firm growth are perfectly correlated within a firm, then the growth rates of small and large firms are equally volatile, contrary to what is found in the data. If firm growth is the result of many independent shocks within a firm, it can take hundreds of years for a few large firms to emerge. This paper describes an economy with both types of shocks that can account for the thick-tailed firm size distribution, high entry and exit rates, and the relatively young age of large firms. The economy is one in which aggregate growth is driven by the creation of new products by both new and incumbent firms. Some new firms have better ideas than others and choose to implement those ideas at a more rapid pace. Eventually, such firms slow down when the quality of their ideas reverts to the mean. As in the data, average growth rates in a cross section of firms will appear to be independent of firm size, for all but the smallest firms.

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.

No abstract available.

An examination of the behavior of stock returns around quarterly earnings announcement dates finds a seasonal pattern: small firms show large positive abnormal returns and a sizable increase in the variability of returns around these dates. Only part of the large abnormal returns can be accounted for by the fact that firms with good news tend to announce early. Large firms show no abnormal returns around announcement dates and a much smaller increase in variability.

This paper presents a simple model of government reputation which captures two characteristics of policy outcomes in less developed countries: governments which betray public trust do so erratically, and, after a betrayal, public trust is regained only gradually.

Between the sixties and the late eighties the percentages of low-saving single-parent households and people living alone have grown dramatically at the expense of high-saving married households, while the household saving rate has declined equally dramatically. A preliminary analysis of population composition and savings by household type seems to indicate that about half of the decline in savings is due to demographic change. We construct a model with agents changing marital status, but where the saving behavior of the households can adjust to the properties of the demographic process. We find that the demographic changes that reduce the number of married households (mainly higher divorce and higher illegitimacy) induce all household types to save more and that the effect on the aggregate saving rate is minuscule. We conclude that the drop in savings since the sixties is not due to changes in household composition.

The paper compares implications of three kinds of models of households’ consumption behavior: the basic permanent-income model, several models of liquidity-constrained households, and a model of an informationally-constrained efficient contract. These models are distinguished in terms of implications regarding the present discounted values of net trades to households at various levels of temporary income, and the households’ marginal rates of substitution. Martingale consumption is studied as an approximation to the predicted consumption process of the efficient-contract model.

We extend the baseline Susceptible-Exposed-Infectious-Recovered (SEIR) infectious disease epidemiology model to understand the role of testing and case-dependent quarantine. Our model nests the SEIR model. During a period of asymptomatic infection, testing can reveal infection that otherwise would only be revealed later when symptoms develop. Along with those displaying symptoms, such individuals are deemed known positive cases. Quarantine policy is case-dependent in that it can depend on whether a case is unknown, known positive, known negative, or recovered. Testing therefore makes possible the identification and quarantine of infected individuals and release of non-infected individuals. We fix a quarantine technology - a parameter determining the differential rate of transmission in quarantine - and compare simple testing and quarantine policies. We start with a baseline quarantine-only policy that replicates the rate at which individuals are entering quarantine in the US in March, 2020. We show that the total deaths that occur under this policy can be achieved under looser quarantine measures and a substantial increase in random testing of asymptomatic individuals. Testing at a higher rate in conjunction with targeted quarantine policies can (i) dampen the economic impact of the coronavirus and (ii) reduce peak symptomatic infections - relevant for hospital capacity constraints. Our model can be plugged into richer quantitative extensions of the SEIR model of the kind currently being used to forecast the effects of public health and economic policies.

This paper presents a continuous-time model of sovereign debt. In it, a relatively impatient sovereign government’s hidden type switches back and forth between a commitment type, which cannot default, and an optimizing type, which can default on the country’s debt at any time, and assume outside lenders have particular beliefs regarding how a commitment type should borrow for any given level of debt and bond price. We show that if these beliefs satisfy reasonable assumptions, in any Markov equilibrium, the optimizing type mimics the commitment type when borrowing, revealing its type only by defaulting on its debt at random times. Further, in such Markov equilibria (the solution to a simple pair of ordinary differential equations), there are positive gross issuances at all dates, constant net imports as long as there is a positive equilibrium probability that the government is the optimizing type, and net debt repayment only by the commitment type. For countries that have recently defaulted, the interest rate the country pays on its debt is a decreasing function of the amount of time since its last default, and its total debt is an increasing function of the amount of time since its last default. For countries that have not recently defaulted, interest rates are constant.