In order to share risk, protection buyers trade derivatives with protection sellers. Protection sellers’ actions affect the riskiness of their assets, which can create counterparty risk. Because these actions are unobservable, moral hazard limits risk sharing. To mitigate this problem, privately optimal derivative contracts involve variation margins. When margins are called, protection sellers must liquidate some assets, depressing asset prices. This tightens the incentive constraints of other protection sellers and reduces their ability to provide insurance. Despite this fire-sale externality, equilibrium is information-constrained efficient. Investors, who benefit from buying assets at fire-sale prices, optimally supply insurance against the risk of fire sales.

We develop a model of interbank lending and borrowing with counterparty risk. The model has two key ingredients. First, liquidity in the banking sector is endogenous, so there is an opportunity cost of holding liquid assets. Second, banks are privately informed about the risk of their long-term assets, which can lead to adverse selection and high interest rates in the interbank market. We identify a novel form of a market break-down, which can lead to liquidity hoarding. It arises because adverse selection in the interbank market changes the opportunity cost of holding liquidity. We use the model to shed light on developments in interbank markets prior to and during the 2007–09 financial crisis, as well as the effectiveness of policy interventions aimed at restoring interbank market activity.

Derivatives activity, motivated by risk‐sharing, can breed risk‐taking. Bad news about the risk of an asset underlying a derivative increases protection sellers' expected liability and undermines their risk‐prevention incentives. This limits risk‐sharing, creates endogenous counterparty risk, and can lead to contagion from news about the hedged risk to the balance sheet of protection sellers. Margin calls after bad news can improve protection sellers' incentives and in turn enhance risk‐sharing. Central clearing can provide insurance against counterparty risk but must be designed to preserve risk‐prevention incentives.

Building on intuition from the dynamic asset pricing literature, we uncover unobserved risk aversion and fundamental uncertainty from the observed time series of the variance premium and the credit spread while controlling for the conditional variance of stock returns, expectations about the macroeconomic outlook, and interest rates. We apply this methodology to monthly data from both Germany and the US. We find that the variance premium contains a substantial amount of information about risk aversion whereas the credit spread has a lot to say about uncertainty. We link our risk aversion and uncertainty estimates to practitioner and “academic” risk aversion indices, sentiment indices, financial stress indices, business cycle indicators and liquidity measures.

We measure the commonality in hedge fund returns, identify its main driving factor and analyze its implications for financial stability. We find that hedge funds’ commonality increased significantly from 2003 until 2006. We attribute this rise mainly to the increase in hedge funds’ exposure to emerging market equities, which we identify as a common factor in hedge fund returns over this period. Our results show that funds with a high commonality were affected disproportionately by illiquidity and exhibited negative returns during the subsequent financial crisis, thereby providing little diversification benefits to the financial system and to investors.

This paper investigates the impact of ample liquidity provision by the European Central Bank on the functioning of the overnight unsecured interbank market from 2008 to 2014. We use novel data on interbank transactions derived from TARGET2, the main euro area payment system. To identify exogenous shocks to central bank liquidity, we exploit the timing of ECB liquidity operations and use a simple structural vector auto-regression framework. We argue that the ECB acted as a de facto lender-of-last-resort to the euro area banking system and identify two main effects of central bank liquidity provision on interbank markets. First, central bank liquidity replaces the demand for liquidity in the interbank market, especially during the financial crisis (2008–2010). Second, it increases the supply of liquidity in the interbank market in stressed countries (Greece, Italy and Spain) during the sovereign debt crisis (2011–2013).

We document dramatic changes in euro area interbank money markets during the financial and sovereign debt crises: unsecured borrowing declined across the euro area, while secured market haircuts on sovereign bonds increased, and bank borrowing from the European Central Bank rose in southern countries. We construct a quantitative general equilibrium model to assess the macroeconomic impact of these developments and the associated policy response. Our model features heterogeneous banks and sovereign bonds, secured and unsecured money markets, and a central bank. We compare a benchmark policy—the central bank providing collateralized lending to banks at haircuts lower than the market—with an alternative policy that maintains a constant central bank balance sheet. We show that the fall in output, investment, and capital would have been twice as high under the alternative policy.