The existence of mean-variance efficient positive portfolios – portfolios with no negative weights – is a key requirement for equilibrium in the Capital Asset Pricing Model (CAPM). Brennan and Lo (2010) define an “impossible frontier” as a frontier on which all portfolios have at least one negative weight. They prove that for randomly drawn covariance matrices the probability of obtaining an im...

In this paper, we develop a new capital adequacy buffer model (CABM) which is sensitive to dynamic economic circumstances. The model, which measures additional bank capital required to compensate for fluctuating credit risk, is a novel combination of the Merton structural model, which measures distance to default, and the timeless capital asset pricing model (CAPM) which measures additional ret...

We show that Black Capital Asset Pricing Model (Black CAPM) is extremely sensitive to the choice of the market portfolio and becomes unstable as market portfolios approach the Global Minimum-Variance portfolio. When market portfolios approach the minimum-variance portfolio, the expected return on the zero beta asset approaches negative infinity and its variance increases rapidly. Moreover, expe...

Finance theory can be used to form informative prior beliefs in financial decision making. This paper approaches portfolio selection in a Bayesian framework that incorporates a prior degree of belief in an asset pricing model. Sample evidence on home bias and value and size effects is evaluated from an asset-allocation perspective. U.S. investors' belief in the domestic CAPM must be very strong...

We generalize the Arbitrage Pricing Theory (APT) to include the contribution of virtual arbitrage opportunities. We model the arbitrage return by a stochastic process. The latter is incorporated in the APT framework to calculate the correction to the APT due to the virtual arbitrage opportunities. The resulting relations reduce to the APT for an infinitely fast market reaction or in the case wh...

Firm-level studies of the financial impacts of Information Technology (IT) events have often focused on announcement period returns based on the capital asset pricing model (CAPM). This approach may have two sets of distinct but related limitations for many classes of IT events. First, the use of announcement period assumes the market is efficient in its assimilation and pricing of all informat...

modern portfolio theories are based on markowitz’s portfolio optimization model that involves the assumption of mean variance behavior and therefore require the asymmetry and normality of returns. this issue also affects the capital asset pricing model that estimates systematic risk and uses it in pricing securities. this article analyzes the various measures of risk. the main purpose of this r...

This study documents the asset pricing mechanism of Sharīʿah compliant securities listed on the Karachi Stock Exchange. We select the CAPM market model to test for the impact in variations of stock returns on a sample of Sharīʿah-compliant companies on ten years monthly data (2001-10). We first test the basic CAPM (Capital Asset Pricing Model) and its modified form known as the Sharīʿah-complia...

We propose an errors-in-variables factor model which extends the classical capital asset pricing model (CAPM) to the case where the market returns contain additive noise. Using the model, we propose a method for choosing portfolios of assets, such as U.S. stocks in the S&P 100 and virtual electricity contracts in a regional transmission organization. Virtual electricity contracts relate real-ti...

longer follow. The capital asset pricing model (CAPM) is an elegant theory. With the aid of some simplifying assumptions, it comes to dramatic conclusions about practical matters, such as how to choose an investment portfolio, how to forecast the expected return of a security or asset class, how to price a new security, or how to price risky assets in a merger or acquisition. The CAPM starts wi...