A Theory of Foreign Exchange Interventions

We study a real small open economy with two key ingredients (1) partial segmentation of home and foreign bond markets and (2) a pecuniary externality that makes the real exchange rate excessively volatile in response to capital flows. Partial segmentation implies that, by intervening in the bond markets, the central bank can affect the exchange rate and the spread between home- and foreign-bond yields. Such interventions allow the central bank to address the pecuniary externality, but they are also costly, as foreigners make carry trade profits. We analytically characterize the optimal intervention policy that solves this trade-off: (1) the optimal policy leans against the wind, stabilizing the exchange rate; (2) it involves smooth spreads but allows exchange rates to jump; (3) it partly relies on “forward guidance,” with non-zero interventions even after the shock has subsided; (4) it requires credibility, in that central banks do not intervene without commitment. Finally, we shed light on the global consequences of widespread interventions, using a multi-country extension of our model. We find that, left to themselves, countries over-accumulate reserves, reducing welfare and leading to inefficiently low world interest rates.

General Equilibrium Oligopoly and Ownership Structure

We develop a tractable general equilibrium framework in which firms are large and have market power with respect to both products and labor, and in which a firm's decisions are affected by its ownership structure. We characterize the Cournot–Walras equilibrium of an economy where each firm maximizes a share‐weighted average of shareholder utilities—rendering the equilibrium independent of price normalization. In a one‐sector economy, if returns to scale are non‐increasing, then an increase in “effective” market concentration (which accounts for common ownership) leads to declines in employment, real wages, and the labor share. Yet when there are multiple sectors, due to an intersectoral pecuniary externality, an increase in common ownership could stimulate the economy when the elasticity of labor supply is high relative to the elasticity of substitution in product markets. We characterize for which ownership structures the monopolistically competitive limit or an oligopolistic one is attained as the number of sectors in the economy increases. When firms have heterogeneous constant returns to scale technologies, we find that an increase in common ownership leads to markets that are more concentrated.

Financial Amplification of Labor Supply Shocks

We study how financial frictions amplify labor supply shocks in a macroeconomic model with occasionally binding financing constraints. Workers supply labor to entrepreneurs who borrow to purchase factors of production. Borrowing capacity is restricted by the value of capital, generating a pecuniary externality when financing constraints bind. Additionally, there is a distributive externality operating through wages. The planner’s allocation can be decentralized with two instruments: a credit tax/subsidy and a labor tax/subsidy. Labor shocks, such as the COVID-19 shock, amplify the policy responses, which critically depend on whether financing constraints bind or not.

Bank Leverage and Social Welfare

We describe a general equilibrium model in which an agency problem arises because bankers must exert an unobserved and costly effort to perform their task. Suppose aggregate banker net worth is too low to insulate creditors from bad outcomes on their balance sheet. Then, banks borrow too much in equilibrium because there is a pecuniary externality associated with bank borrowing. Social welfare is increased by imposing a binding leverage restriction on banks. We formalize this argument and provide a numerical example.

On the Optimal Inflation Rate

In our incomplete markets economy households choose portfolios consisting of risky (uninsurable) capital and money. Money is a bubble, it has positive value even though it yields no payoff. The market outcome is constrained Pareto inefficient due to a pecuniary externality. Each individual agent takes the real interest rate as given, while in the aggregate it is driven by the economic growth rate, which in turn depends on individual portfolio decisions. Higher inflation due to higher money growth lowers the real interest rate on money and tilts the portfolio choice towards physical capital investment. Modest inflation boosts growth rate and welfare.

Excessive Financing Costs in a Representative Agent Framework

This paper highlights a pecuniary externality that results in excessive financing costs. Firms borrow to finance purchases of an inelastically supplied input, bidding up its price. Since higher input prices necessitate more debt obligations, this leads to an increase in intermediation costs. A quantitative interpretation of the model suggests that it is optimal to tax financial intermediation by increasing the borrowing rate by 3 percentage points. (JEL E13, E44, G21, G32, H21, H25)

The Role of Proximity in Foreclosure Externalities: Evidence from Condominiums

We measure the effect of foreclosures on the sale prices of nearby properties using a dataset of condominiums in Boston. A foreclosure in the same association and at the same address depresses the sale price by 2.5 percent, but properties in the same association but located at a different address have an effect that is tightly estimated at zero. Since properties in the same association are close substitutes, we argue that the evidence points against the pecuniary externality of property coming on the market and toward a physical externality as the source of measured foreclosure externalities. (JEL R31)