Dimitri Vayanos

Quantitative Easing and Unconventional Monetary Policy – An Introduction

This article assesses the impact of Quantitative Easing and other unconventional monetary policies followed by central banks in the wake of the financial crisis that began in 2007. We consider the implications of theoretical models for the effectiveness of asset purchases and look at the evidence from a range of empirical studies. We also provide an overview of the contributions of the other articles in this Feature.

The Gambler's and Hot-Hand Fallacies: Theory and Applications

We develop a model of the gamblers fallacy (the mistaken belief that random sequences should exhibit systematic reversals). We show that an individual who holds this belief and observes a sequence of signals can exaggerate the magnitude of changes in an underlying state but underestimate their duration. When the state is constant, and so signals are i.i.d., the individual can predict that long streaks of similar signals will continue { a hot-hand fallacy. When signals are serially correlated, the individual typically under-reacts to short streaks, over-reacts to longer ones, and under-reacts to very long ones. We explore several applications, showing, for example, that investors may move assets too much in and out of mutual funds, and exaggerate the value of financial information and expertise.

Strategic Trading and Welfare in a Dynamic Market

This paper studies a dynamic model of a financial market with N strategic agents. Agents receive random stock endowments at each period and trade to share dividend risk. Endowments are the only private information in the model. We find that agents trade slowly even when the time between trades goes to 0. In fact, welfare loss due to strategic behaviour increases as the time between trades decreases. In the limit when the time between trades goes to 0, welfare loss is of order 1/N, and not 1/N2 as in the static models of the double auctions literature. The model is very tractable and closed-form solutions are obtained in a special case.

Strategic trading in a dynamic noisy market

This paper studies a dynamic model of a financial market with a strategic trader. In each period the strategic trader receives a privately observed endowment in the stock. He trades with competitive market makers to share risk. Noise traders are present in the market. After receiving a stock endowment, the strategic trader is shown to reduce his risk exposure either by selling at a decreasing rate over time or by selling and then buying back some of the shares sold. When the time between trades is small, the strategic trader reveals the information regarding his endowment very quickly.

Market Liquidity -- Theory and Empirical Evidence

In this paper we survey the theoretical and empirical literature on market liquidity. We organize both literatures around three basic questions: (a) how to measure illiquidity, (b) how illiquidity relates to underlying market imperfections and other asset characteristics, and (c) how illiquidity affects expected asset returns. Using a unified model from Vayanos and Wang (2010), we survey theoretical work on six main imperfections: participation costs, transaction costs, asymmetric information, imperfect competition, funding constraints, and search—and for each imperfection we address the three basic questions within that model. We review the empirical literature through the lens of the theory, using the theory to both interpret existing results and suggest new tests and analysis.

The Sovereign-Bank Diabolic Loop and ESBies

We propose a simple model of the sovereign-bank diabolic loop, and establish four results. First, the diabolic loop can be avoided by restricting banks’ domestic sovereign exposures relative to their equity. Second, equity requirements can be lowered if banks only hold senior domestic sovereign debt. Third, such requirements shrink even further if banks only hold the senior tranche of an internationally diversified sovereign portfolio – known as ESBies in the euro-area context. Finally, ESBies generate more safe assets than domestic debt tranching alone; and, insofar as the diabolic loop is defused, the junior tranche generated by the securitization is itself risk-free.

Preferred - Habitat Investors and the US Term Structure of Real Rates

We estimate structurally a model of the term structure of interest rates that is consistent with no arbitrage but allows for demand pressures. The term structure in our model is determined through the interaction of risk-averse arbitrageurs and preferred-habitat investors with preferences for specific maturities. The model is estimated on US real rates during the 2000s and allows for two factors: one corresponding to the short rate and one to preferred-habitat demand. We find that the puzzling drop in long rates during 2004-05 (Greenspan conundrum) is driven by the demand factor, which in turn is correlated with purchases of long-term bonds by foreign officials. For example, foreign purchases in July 2004 appear to have lowered the 10-year rate by about 100 basis points. Foreign purchases have larger effects following periods when arbitrageurs have lost money.

Theories of Liquidity

We survey the theoretical literature on market liquidity. The literature traces illiquidity, i.e., the lack of liquidity, to underlying market imperfections. We consider six main imperfections: participation costs, transaction costs, asymmetric information, imperfect competition, funding constraints, and search. We address three questions in the context of each imperfection: (a) how to measure illiquidity, (b) how illiquidity relates to underlying market imperfections and other asset characteristics, and (c) how illiquidity affects expected asset returns. We nest all six imperfections within a common, unified model, and use that model to organize the literature.

ESBies: safety in the tranches

The euro crisis was fueled by the diabolic loop between sovereign risk and bank risk, coupled with cross-border flight-to-safety capital flows. European Safe Bonds (ESBies), a union-wide safe asset without joint liability, would help to resolve these problems. We make three contributions. First, numerical simulations show that ESBies would be at least as safe as German bunds and approximately double the supply of euro safe assets when protected by a 30%-thick junior tranche. Second, a model shows how, when and why the two features of ESBies — diversification and seniority — can weaken the diabolic loop and its diffusion across countries. Third, we propose a step-by-step guide on how to create ESBies, starting with limited issuance by public or private-sector entities.

The Dynamics of Financially Constrained Arbitrage

We develop a model of financially constrained arbitrage, and use it to study the dynamics of arbitrage capital, liquidity, and asset prices. Arbitrageurs exploit price discrepancies between assets traded in segmented markets, and in doing so provide liquidity to investors. A collateral constraint limits their positions as a function of capital. We show that the dynamics of arbitrage activity are self-correcting: following a shock that depletes arbitrage capital, profitability increases, and this allows capital to be gradually replenished. Spreads increase more and recover faster for more volatile trades, although arbitrageurs cut their positions in these trades the least. When arbitrage capital is more mobile across markets, liquidity in each market generally becomes less volatile, but the reverse may hold for aggregate liquidity because of mobility-induced contagion.