Research Database

We describe a model for calculating the optimal quantity of debt and then apply it to the U.S. economy. The model consists of a large number of infinitely-lived households whose saving behavior is influenced by precautionary saving motives and borrowing constraints. This model incorporates a different role for government debt than the standard representative agent growth model and captures different trade-offs between the benefits and costs of varying its level. Government debt enhances the liquidity of households by providing additional assets for smoothing consumption (in addition to claims to capital) and effectively loosening borrowing constraints. By raising the interest rate, government debt makes assets less costly to hold and more effective in smoothing consumption. However, the implied taxes have wealth distribution, incentive, and insurance effects. Further, government debt crowds out capital (via higher interest rates) and lowers per capita consumption. Our quantitative analysis suggests that the crowding out effect is decisive for welfare. We also describe variations of the model which permit endogenous growth. It turns out that even with lump sum taxes and inelastic labor, government debt as well as government consumption have growth rate effects, thereby implying large welfare gains from reducing the level of debt.

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.

This paper establishes the stylized fact that medieval debasements were accompanied by unusually large minting volumes and revenues. This fact is a puzzle under the commonly held view that metallic coins are commodity money and exchange by weight. An existing explanation is that debased coins were used to reduce the real burden of nominally denominated debts. This explanation is logically flawed: nothing prevents agents from renegotiating contracts and avoid incurring minting costs. The paper also establishes other facts about monetary mutations, which altogether pose a challenge to monetary economics.

In empirical studies of the CAPM, it is commonly assumed that (a) the return to the value weighted portfolio of all stocks is a reasonable proxy for the return on the market portfolio of all assets in the economy, and (b) betas of assets remain constant over time. Under these assumptions, Fama and French (1992) find that the relation between average return and beta is flat. We argue that these two auxiliary assumptions are not reasonable. We demonstrate that when these assumptions are relaxed, the empirical support for the CAPM is surprisingly strong. When human capital is also included in measuring wealth, the CAPM is able to explain 28 percent of the cross sectional variation in average returns in the 100 portfolios studied by Fama and French. When, in addition, betas are allowed to vary over the business cycle, the CAPM is able to explain 57 percent. More important, relative size does not explain what is left unexplained after taking sampling errors into account.

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.

In this paper we construct a stochastic overlapping-generations general equilibrium model in which households are subject to aggregate shocks that affect both wages and asset prices. We use a calibrated version of the model to quantify how the welfare costs of severe recessions are distributed across different household age groups. The model predicts that younger cohorts fare better than older cohorts when the equilibrium decline in asset prices is large relative to the decline in wages, as observed in the data. Asset price declines hurt the old, who rely on asset sales to finance consumption, but benefit the young, who purchase assets at depressed prices. In our preferred calibration, asset prices decline more than twice as much as wages, consistent with the experience of the US economy in the Great Recession. A model recession is approximately welfare-neutral for households in the 20–29 age group, but translates into a large welfare loss of around 10% of lifetime consumption for households aged 70 and over.