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We explore how large and small banks make funding decisions when system-wide bailouts are possible. We show that bank size, purely on strategic grounds, is a key determinant of banks’ leverage choices, even when bailout policies treat large and small banks symmetrically. Large banks leverage more than small banks because they internalize that their decisions directly affect bailout policies. In equilibrium, this effect is amplified by strategic spillovers to small banks since banks’ leverage choices are strategic complements. Overall, the presence of large banks makes bailouts more likely. The optimal regulation features size-dependent policies that disproportionately restrict large banks’ leverage.

This paper studies the optimal design of second-best corrective regulation, when some agents or activities cannot be perfectly regulated. We show that policy elasticities and Pigouvian wedges are sufficient statistics to characterize the marginal welfare impact of regulatory policies in a large class of environments. We show that the optimal second-best policy is determined by a subset of policy elasticities: leakage elasticities, and characterize the marginal value of relaxing regulatory constraints. We apply our results to scenarios with unregulated agents/activities and with uniform regulation across agents/activities. We illustrate our results in applications to shadow banking, scale-invariant regulation, asset substitution, and fire sales. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

This paper studies leverage regulation and monetary policy when equity investors and/or creditors have distorted beliefs relative to a planner. We characterize how the optimal leverage regulation responds to arbitrary changes in investors' and creditors' beliefs and relate our results to practical scenarios. We show that the optimal regulation depends on the type and magnitude of such changes. Optimism by investors calls for looser leverage regulation, while optimism by creditors, or jointly by both investors and creditors, calls for tighter leverage regulation. Monetary policy should be tightened (loosened) in response to either investors' or creditors' optimism (pessimism).

This paper studies the optimal determination of deposit insurance when bank runs are possible. We show that the welfare impact of changes in the level of deposit insurance coverage can be generally expressed in terms of a small number of sufficient statistics, which include the level of losses in specific scenarios and the probability of bank failure. We characterize the wedges that determine the optimal ex-ante regulation, which map to asset- and liability-side regulation. We demonstrate how to employ our framework in an application to the most recent change in coverage, which took place in 2008.

This paper characterizes the optimal transaction tax in an equilibrium model of competitive financial markets. As long as investors hold heterogeneous beliefs that are not related to their fundamental trading motives and the planner calculates welfare using any single belief, a strictly positive tax is optimal, regardless of the magnitude of fundamental trading. Under some conditions, the optimal tax is independent of the belief used by the planner to calculate welfare. The optimal tax can be implemented by adjusting its value until observed total volume equals fundamental volume. Knowledge of i) the share of non-fundamental trading volume and ii) the semi-elasticity of trading volume to tax changes is sufficient to quantify the optimal tax. A calibration of the model consistent with empirically estimated volume semi-elasticities to tax changes and that features a 30% share of non-fundamental trading volume is associated with a 37bps optimal tax. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

This paper studies the optimal determination of deposit insurance (DI) when bank runs are possible. In a variety of environments, the welfare impact of changes in the level of deposit insurance coverage exclusively depends on three sufficient statistics: the sensitivity of the likelihood of bank failure with respect to the level of DI, the utility gain induced by preventing the marginal bank failure, which can be expressed in terms of the drop in depositors' consumption, and the direct social cost of intervention in bank failure scenarios, which can be expressed in terms of the probability of bank failure, the marginal cost of public funds, and the mass of partially insured depositors. The same expression applies a) when banks face perfect ex-ante regulation and b) when banks are not allowed to react to policy changes. Under imperfect regulation, because banks do not internalize the fiscal impact of their actions, changes in the behavior of banks induced by varying the level of DI (often referred to as moral hazard) only affect the level of optimal DI directly through a fiscal externality, but not independently. We characterize the wedges that determine the optimal ex-ante regulation, which map to liability-side regulation (e.g., deposit insurance premia) and asset-side regulation. Finally, we explore the quantitative implications of our approach through a direct measurement exercise and a model simulation.

This paper studies financial and monetary policy in environments in which equity investors and creditors may have distorted beliefs. We characterize conditions under which it is optimal to tighten or relax leverage caps in response to arbitrary changes in beliefs. The optimal policy response to belief distortions depends on the type as well as the extent of exuberance, and it is not generally true that regulators should lean against the wind by tightening leverage caps in response to optimism. We show that increased optimism by investors is associated with relaxing the optimal leverage cap, while increased optimism by creditors, or jointly by both investors and creditors is associated with a tighter optimal leverage cap. In the presence of government bailouts, increased optimism by equity investors may call for a tighter optimal leverage cap too, depending on whether equity optimism is concentrated on upside or downside risk. Increased optimism by either equity investors or creditors is associated with higher incentives to raise interest rates, so monetary tightening can act as a useful substitute for financial regulation.

This article characterizes the efficiency properties of competitive economies with financial constraints, in which phenomena such as fire sales and financial amplification may arise. We show that financial constraints lead to two distinct types of pecuniary externalities: distributive externalities that arise from incomplete insurance markets and collateral externalities that arise from price-dependent financial constraints. For both types of externalities, we identify three sufficient statistics that determine optimal taxes on financing and investment decisions to implement constrained efficient allocations. We also show that fire sales and financial amplification are neither necessary nor sufficient to generate inefficient pecuniary externalities. We demonstrate how to employ our framework in a number of applications. Whereas collateral externalities generally lead to over-borrowing, the distortions from distributive externalities may easily flip sign, leading to either under- or over-borrowing. Both types of externalities may lead to under- or over-investment.

This article studies the optimal determination of bankruptcy exemptions for risk averse borrowers who use unsecured contracts but have the possibility of defaulting. In a large class of economies, knowledge of four variables is sufficient to determine whether a bankruptcy exemption level is optimal or should be increased or decreased. These variables are 1. the composition of households’ liabilities, 2. the sensitivity of the credit supply schedule to exemption changes, 3. the probability of filing for bankruptcy with non-exempt assets, and 4. the value given by households to a marginal dollar in different states, which can be mapped to changes in households’ consumption. I recover empirical estimates of the sufficient statistics using U.S. data over the period 2008–16 and find that increasing exemption levels improves overall welfare, although there is substantial variation in estimated welfare gains across U.S. states and income quintiles.

We explore the equilibrium relation between price volatility and price informativeness in financial markets, with the ultimate goal of characterizing the type of inferences that can be drawn about price informativeness by observing price volatility. We identify two different channels (noise reduction and equilibrium learning) through which changes in price informativeness are associated with changes in price volatility. We show that when informativeness is sufficiently high (low) volatility and informativeness positively (negatively) comove in equilibrium for any change in primitives. In the context of our leading application, we provide conditions on primitives that guarantee that volatility and informativeness always comove positively or negatively. We use data on U.S. stocks between 1963 and 2017 to recover stock-specific primitives and find that most stocks lie in the region of the parameter space in which informativeness and volatility comove negatively.

We show that outcomes (parameter estimates and R-squareds) of regressions of prices on fundamentals allow us to recover exact measures of the ability of asset prices to aggregate dispersed information. Formally, we show how to recover absolute and relative price informativeness in dynamic environments with rich heterogeneity across investors (regarding signals, private trading needs, or preferences), minimal distributional assumptions, multiple risky assets, and allowing for stationary and non-stationary asset payoffs. We implement our methodology empirically, finding stock-specific measures of price informativeness for U.S. stocks. We find a right-skewed distribution of price informativeness, measured in the form of the Kalman gain used by an external observer that conditions its posterior belief on the asset price. The recovered mean and median are 0.05 and 0.02 respectively. We find that price informativeness is higher for stocks with higher market capitalization and higher trading volume.

We study the relationship between homebuyers’ beliefs about future house price changes and their mortgage leverage choices. Whether more pessimistic homebuyers choose higher or lower leverage depends on their willingness and ability to reduce the size of their housing market investments. When households primarily maximize the levered return of their property investments, more pessimistic homebuyers reduce their leverage to purchase smaller houses. On the other hand, when considerations such as family size pin down the desired property size, pessimistic homebuyers reduce their financial exposure to the housing market by making smaller downpayments to buy similarly-sized homes. To determine which scenario better describes the data, we investigate the cross-sectional relationship between house price beliefs and mortgage leverage choices in the U.S. housing market. We use plausibly exogenous variation in house price beliefs to show that more pessimistic homebuyers make smaller downpayments and choose higher leverage, in particular in states where default costs are relatively low, as well as during periods when house prices are expected to fall on average. Our results highlight the important role of heterogeneous beliefs in explaining households’ financial decisions