Belief Disagreements and Collateral Constraints

Belief disagreements have been suggested as a major contributing factor to the recent financial crisis. This paper theoretically evaluates this hypothesis. I assume that optimists have limited wealth and take on leverage in order to take positions in line with their beliefs. To have a significant effect on asset prices, they need to borrow from traders with pessimistic beliefs using loans collateralized by the asset itself. Since pessimists do not value the collateral as much as optimists do, they are reluctant to lend, which provides an endogenous constraint on optimist's ability to borrow and to influence asset prices. I demonstrate that the tightness of this constraint depends on the nature of belief disagreements. Optimism concerning the probability of downside states has no or little effect on asset prices because these types of optimism are disciplined by this constraint. Instead, optimism concerning the relative probability of upside states could have significant effects on asset prices. This asymmetric disciplining effect is robust to allowing for short selling because pessimists that borrow the asset face a similar endogenous constraint. These results emphasize that what investors disagree about matters for asset prices, to a greater extent than the level of disagreements. When richer contracts are available, insurance contracts (similar to credit default swaps) endogenously emerge to facilitate betting. Richer contracts moderate the effect of belief disagreements on asset prices because the medium of betting shifts from buying (or shorting) the asset to trading alternative contracts.Economic

Complexity and financial panics

May 15, 2009. Revision: June 17, 200

Moral hazard and efficiency in general equilibrium with anonymous trading

April 27, 200

Fire sales in a model of complexity

October 28, 200

Speculation 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 the average variance that would obtain if there were no belief disagreements, and the speculative variance, defined as the residual variance that results from speculative trades based on belief disagreements. Financial innovation always decreases the uninsurable variance because new assets increase the possibilities for risk sharing. My main result shows that financial innovation also always increases the speculative variance. This is true even if traders completely agree about the payoffs of new assets. The intuition behind this result is the hedge-more/bet-more effect: Traders use new assets to hedge their bets on existing assets, which in turn enables them to place larger bets and take on greater risks. The net effect of financial innovation on portfolio risks depends on the quantitative strength of its effects on the uninsurable and the speculative variances. I consider a calibration of the model for new assets linked to national incomes of G7 countries, which were recommended by Athanasoulis and Shiller (2001) to facilitate risk sharing. For reasonable levels of belief disagreements, these assets would actually increase the average consumption risks of individuals in G7 countries. In addition, a profit seeking market maker would introduce a different subset of these assets than the ones proposed by Athanasoulis and Shiller (2001). The endogenous set of new assets would be directed towards increasing the opportunities for speculation rather than risk sharing.

Speculation and Risk Sharing with New Financial Assets

I investigate the effect of financial innovation on portfolio risks when traders have belief disagreements. I decompose traders’ average portfolio risks into two components: the uninsurable variance, defined as portfolio risks that would obtain without belief disagreements, and the speculative variance, defined as portfolio risks that result from speculation. My main result shows that financial innovation always increases the speculative variance through two distinct channels: by generating new bets and by amplifying traders’ existing bets. When disagreements are large, these effects are sufficiently strong that financial innovation increases average portfolio risks, decreases average portfolio comovements, and generates greater speculative trading volume relative to risk-sharing volume. Moreover, a profit-seeking market maker endogenously introduces speculative assets that increase average portfolio risks

Complexity and Financial Panics

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 partners of the trading partners of the trading partners, and so on. At some point, the cost of information gathering becomes too unmanageable for banks, uncertainty spikes, and they have no option but to withdraw from loan commitments and illiquid positions. A flight-to-quality ensues, and the financial crisis spreads.

Fire Sales in a Model of Complexity

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 brings about confusion and uncertainty, which makes relatively healthy banks, and hence potential asset buyers, reluctant to buy since they now fear becoming embroiled in a cascade they do not control or understand. The liquidity of the market quickly vanishes and a financial crisis ensues. The model exhibits a powerful “complexity-externality.” As a potential asset buyer chooses to pull back, the size of the cascade grows, which increases the degree of complexity of the environment. This rise in perceived complexity induces other healthy banks to pull back, which exacerbates the fire sale and the cascade.

The Choice Channel of Financial Innovation

Financial innovation in recent decades has expanded portfolio choice. We investigate how greater choice affects investors' savings and asset returns. We establish a choice channel by which greater portfolio choice increases investors' savings—by enabling them to earn the aggregate risk premium or take speculative positions. In equilibrium, portfolio customization (access to risky assets beyond the market portfolio) reduces the risk-free rate. Participation (access to the market portfolio) reduces the risk premium but typically increases the risk-free rate. Empirically, stock market participants in the United States save more than nonparticipants and have increasingly dispersed portfolio returns, consistent with the choice channel.acceptedVersio