Knowledge that Transforms

Under the assumptions of the Consumption-based Capital Asset Pricing Model (CCAPM), Pareto optimal consumption allocations are characterized by each agent's consumption process being adapted to the filtration generated by the aggregate consumption process of the economy. The wealth processes of the agents, however, are adapted to the finer filtration generated by aggregate consumption and the conditional distribution of future aggregate consumption. Therefore, in order to achieve pareto optimal consumption allocations, a sufficiently varied set of assets must exist such that any wealth process adapted to this finer filtration can be implemented by dynamically trading in that set of assets. We provide sufficient conditions for the existence of such a set of assets based on dynamically trading contingent claims on aggregate consumption. In addition, we give sufficient conditions for the existence of equilibria in a dynamically effectively complete market in which agents are only able to trade in contingent claims on aggregate consumption, the market portfolio of firms, and a (numeraire) zero-coupon bond. We demonstrate the role of short- and long-term contingent claims on aggregate consumption for the implementation of Pareto optimal allocations inthe presence of short- and long-term risks. In addition, in the presence of personal risks, we demonstrate the role of insurance contracts. JEL Classification: G13.

This paper analyzes how an investor who is convinced that he can “beat the market” should behave when the equilibrium price process is endogenous. The investor's optimal portfolio is shown to consist of three components: (1) a tangency portfolio, (2) a hedge portfolio against changes in the market's valuation of securities, and (3) a hedging position against changes in the divergence between the investor's and the market's beliefs. The sign and magnitude of this third component will depend on investor preferences and on the divergence in the investor's and the market's quality of information. A numerical example illustrates that the effect of heterogeneous beliefs on optimal portfolio allocations can be significant. JEL classification codes: G11, G14.

The effect of incomplete information on the term structure of interest rates is examined in the framework of a pure exchange economy under uncertainty where aggregate output grows at a constant rate. If the growth rate is known, the term structure is flat. In contrast, the term structure is a decreasing curve when agents do not know the growth rate. Long term yields are less than the short rate and the yield of long term bonds is determined by the worst possible realizations of future short rates. JEL classification codes: D5, D9, E4, G1.

We propose a simple model that is suitable for evaluating alternative bank capital regulatory proposals for market risk. Our model formalizes the conflict between bank objectives and regulatory goals. Banks' decisions represent a tension between their desire to exploit the deposit-insurance put option and their desire to preserve franchise value. Regulators seek to balance the social value of deposits in mediating transactions against the deadweight costs of failure resolution. Our social welfare criterion is standard: a weighted average agents' utilities. We demonstrate that banks do not incrementally alter their portfolio risk as the economic environment changes. Rather, banks either choose the minimal feasible risk or the maximal feasible risk. This pattern, in turn, drives regulatory decisions: The first goal of the regulator is to induce banks to choose the minimal risk level. For all nontrivial cases, unregulated banks fail to choose the first-best allocations. Traditional ex-ante capital requirements can induce banks to choose the socially-optimal level of portfolio risk, but the required capital is often inefficiently high. In contrast, variants of the Federal Reserve Board's precommitment proposal imply far smaller efficiency losses, and achieve allocations at or nearthe first-best for most reasonable model specifications. The ex-post penalties required for the optimal implementation of precommitment are not excessively large. The welfare gains from precommitment are even higher when the precommitment penalty function is precluded from sending banks into default. We conclude that state-contingent regulatory mechanisms, of which the precommitment approach is an example, offer the possibility of substantial gains in regulatory efficiency, relative to traditional state non-contingent regulation.

Pierre Mella-Barral; Comment on ‘Bank Capital Standards for Market Risk: A Welfare Analysis’, Review of Finance, Volume 2, Issue 2, 1 January 1999, Pages 159–16

Value-at-risk methods which employ a linear (“delta only”) approximation to the relation between instrument values and the underlying risk factors are unlikely to be robust when applied to portfolios containing non-linear contracts such as options. The most widely used alternative to the delta-only approach involves revaluing each contract for a large number of simulated values of the underlying factors. In this paper we explore an alternative approach which uses a quadratic approximation to the relation between asset values and the risk factors. This method (i) is likely to be better adapted than the linear method to the problem of assessing risk in portfolios containing non-linear assets, (ii) is less computationally intensive than simulation using full-revaluation and (iii) in common with the delta-only method, operates at the level of portfolio characteristics (deltas and gammas) rather than individual instruments.

The option pricing model has been the work horse in the development of financial economics ever since the seminal papers by Black and Scholes (1973) and Merton (1973). Here, the arbitrage free prices of equity options were derived in closed form. Apart from the price of the underlying asset and contractual terms (strike