NBER Working Papers by Alp Simsek

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Working Papers

March 2014Liquidity Trap and Excessive Leverage
with Anton Korinek: w19970
We investigate the role of macroprudential policies in mitigating liquidity traps driven by deleveraging, using a simple Keynesian model. When constrained agents engage in deleveraging, the interest rate needs to fall to induce unconstrained agents to pick up the decline in aggregate demand. However, if the fall in the interest rate is limited by the zero lower bound, aggregate demand is insufficient and the economy enters a liquidity trap. In such an environment, agents' ex-ante leverage and insurance decisions are associated with aggregate demand externalities. The competitive equilibrium allocation is constrained inefficient. Welfare can be improved by ex-ante macroprudential policies such as debt limits and mandatory insurance requirements. The size of the required intervention depends...
October 2011Speculation and Risk Sharing with New Financial Assets
While the traditional view of financial innovation emphasizes the risk sharing role of new financial assets, belief disagreements about these assets naturally lead to speculation, which represents a powerful economic force in the opposite direction. This paper investigates the effect of financial innovation on portfolio risks in an economy when both the risk sharing and the speculation forces are present. I consider this question in a standard mean-variance framework. Financial assets provide hedging services but they are also subject to speculation because traders do not necessarily agree about their payoffs. I define the average variance of traders' net worths as a measure of portfolio risks for this economy, and I decompose it into two components: the uninsurable variance, defined as th...

Published: “Speculation and Risk Sharing with New Financial Assets,” Quarterly Journal of Economics, Vol. 128-3, p.1365-1396.

November 2009Fire Sales in a Model of Complexity
with Ricardo J. Caballero: w15479
Financial assets provide return and liquidity services to their holders. However, during severe financial crises many asset prices plummet, destroying their liquidity provision function at the worst possible time. In this paper we present a model of fire sales and market breakdowns, and of the financial amplification mechanism that follows from them. The distinctive feature of our model is the central role played by endogenous complexity: As asset prices implode, more “banks” within the financial network become distressed, which increases each (non-distressed) bank’s likelihood of being hit by an indirect shock. As this happens, banks face an increasingly complex environment since they need to understand more and more interlinkages in making their financial decisions. This complexity ...

Published: “Fire Sales in a Model of Complexity,” The Journal of Finance (68): 2549-2587, December 2013 (with Alp Simsek).

May 2009Complexity and Financial Panics
with Ricardo J. Caballero: w14997
During extreme financial crises, all of a sudden, the financial world that was once rife with profit opportunities for financial institutions (banks, for short) becomes exceedingly complex. Confusion and uncertainty follow, ravaging financial markets and triggering massive flight-to-quality episodes. In this paper we propose a model of this phenomenon. In our model, banks normally collect information about their trading partners which assures them of the soundness of these relationships. However, when acute financial distress emerges in parts of the financial network, it is not enough to be informed about these partners, as it also becomes important to learn about the health of their trading partners. As conditions continue to deteriorate, banks must learn about the health of the trading p...

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