ABSTRACT “Limits of Arbitrage” theories hypothesize that the marginal investor in a particular asset market is a specialized arbitrageur rather than a diversified representative investor. We examine the mortgage‐backed securities (MBS) market in this light. We show that the risk of homeowner prepayment, which is a wash in the aggregate, is priced in the MBS market. The covariance of prepayment risk with aggregate wealth implies the wrong sign to match the observed prices of prepayment risk. The price of risk is better explained by a kernel based on MBS market‐wide specific risk, consistent with the specialized arbitrageur hypothesis.

Abstract We develop a model of the global financial cycle with one key ingredient: the international demand for safe dollar assets. The model matches patterns of dollar borrowing and currency mismatch, the U.S. external balance sheet, exorbitant privilege, spillovers of the U.S. monetary policy to the rest of the world, and the dollar as a global risk factor. In doing so, we lay out a novel transmission mechanism through which the U.S. monetary policy affects the currency market and the global economy. The global financial cycle is a dollar cycle.

We model the dynamics of risk premia during crises in asset markets where the marginal investor is a financial intermediary. Intermediaries face an equity capital constraint. Risk premia rise when the constraint binds, reflecting the capital scarcity. The calibrated model matches the nonlinearity of risk premia during crises and the speed of reversion in risk premia from a crisis back to precrisis levels. We evaluate the effect of three government policies: reducing intermediaries borrowing costs, injecting equity capital, and purchasing distressed assets. Injecting equity capital is particularly effective because it alleviates the equity capital constraint that drives the model's crisis. (JEL E44, G12, G21, G23, G24)

ABSTRACT How can mortgages be redesigned to reduce macrovolatility and default? We address this question using a quantitative equilibrium life‐cycle model. Designs with countercyclical payments outperform fixed payments. Among those, designs that front‐load payment reductions in recessions outperform those that spread relief over the full term. Front‐loading alleviates liquidity constraints when they bind most, reducing default and stimulating housing demand. To illustrate, a fixed‐rate mortgage (FRM) with an option to convert to adjustable‐rate mortgage, which front‐loads payment reductions relative to an FRM with an option to refinance underwater, reduces price and consumption declines six times as much and default three times as much.

The United States is currently engulfed in the most severe financial crisis since the Great Depression. The crisis was triggered by the crash in the real estate “bubble” and amplified by the extreme concentration of risk in a highly leveraged financial sector. Conventional wisdom is that both the bubble and the risk concentration were the result of mistakes in regulatory policy: an expansionary monetary policy during the boom period of the bubble, and failure to reign in the practices of unscrupulous lenders. In this paper we argue that, while correct in some dimensions, this story misses two key structural factors behind the securitization process that supported the real estate boom and the corresponding lever age. First, over the last decade, the US has experienced large and sustained capital inflows from foreigners seeking US assets to store value (Caballero, Emmanuel Farhi, and Pierre-Olivier Gourinchas 2008 ). Second, especially after the NASDAQ/tech bubble and bust, excess world savings have looked predominantly for safe debt investments. This should not be surprising because a large amount of the capital flow into the US has been from foreign central banks and governments that are not expert investors and are merely looking for a store of value (Krishnamurthy and Annette Vissing-Jorgenson 2008). In this paper we develop a stylized model that captures the essence of this environment. The model accounts for three facts observed during the boom and bust phases of the current crisis. First, during a period of good shocks— which we interpret as the period up to the end

The last few years have seen a significant re-evaluation of the models used to analyze crises in emerging markets. Recent models typically stress financial constraints or distorted financial incentives. While this certainly represents progress, these models share a weakness with the earlier work: neither is uniquely about emerging markets. Adaptations of the Mundell-Fleming model represent Argentina as a Belgium with larger external shocks. Likewise, emerging market models of financial constraints are adaptations of developed economy ones with tighter financial constraints. In our work, we have advocated a model which distinguishes between the financial constraints affecting borrowing and lending among agents within an emerging economy, and those affecting borrowing from foreign lenders. This 'dual liquidity' model offers a parsimonious description of the behavior of firms, governments, and asset prices during financial crises. It also provides prescriptions for optimal policy responses to these crises.

ABSTRACT Severe flight to quality episodes involve uncertainty about the environment, not only risk about asset payoffs. The uncertainty is triggered by unusual events and untested financial innovations that lead agents to question their worldview. We present a model of crises and central bank policy that incorporates Knightian uncertainty. The model explains crisis regularities such as market‐wide capital immobility, agents' disengagement from risk, and liquidity hoarding. We identify a social cost of these behaviors, and a benefit of a lender of last resort facility. The benefit is particularly high because public and private insurance are complements during uncertainty‐driven crises.

ABSTRACT We propose that the limited financial development of emerging markets is a significant factor behind the large share of dollar‐denominated external debt present in these markets. We show that when financial constraints affect borrowing and lending between domestic agents, agents undervalue insuring against an exchange rate depreciation. Since more of this insurance is present when external debt is denominated in domestic currency rather than in dollars, this result implies that domestic agents choose excessive dollar debt. We also show that limited financial development reduces the incentives for foreign lenders to enter emerging markets. The retarded entry reinforces the underinsurance problem.

ABSTRACT We develop a theory that links the U.S. dollar's valuation in FX markets to the convenience yield that foreign investors derive from holding U.S. safe assets. We show that this convenience yield can be inferred from the Treasury basis, the yield gap between U.S. government and currency‐hedged foreign government bonds. Consistent with the theory, a widening of the basis coincides with an immediate appreciation and a subsequent depreciation of the dollar. Our results lend empirical support to models that impute a special role to the United States as the world's provider of safe assets and the dollar as the world's reserve currency.

ABSTRACT To understand which short‐term debt markets experienced “runs” during the financial crisis, we analyze a novel data set of repurchase agreements (repo), that is, loans between nonbank cash lenders and dealer banks collateralized with securities. Consistent with a run, repo volume backed by private asset‐backed securities falls to near zero in the crisis. However, the reduction is only $182 billion, which is small relative to the stock of private asset‐backed securities as well as the contraction in asset‐backed commercial paper. While the repo contraction is small in aggregate, it disproportionately affected a few dealer banks.