Narrow Results

This paper derives an equilibrium capital asset pricing model (CAPM) in a market with trading constraints and asset price bubbles. The asset price processes are general semimartingales including Markov jump-diffusion processes as special cases, and the trading constraints considered include short sale restrictions, borrowing constraints, and margin requirements, among others. We derive a generalized intertertemporal CAPM and consumption CAPM for these markets. The implications for empirical testing are that additional systematic risk factors will exist in a market with trading constraints and price bubbles as contrasted with an otherwise equivalent unconstrained market with no price bubbles.

In this paper, we revisit the day-of-the-week effect by examining the Taiwan stock market. Based on the daily data from 1991 to 2008, our results show that the Taiwan stock market exhibits a strong day-of-the-week effect. In particular, the return on Tuesday is negative and significant from 1991 to 1997, and the returns on the weekend are positive and significant from 1991 to 1997 and from 2001 to 2008. In agreement with other studies, our results also show that the Tuesday's effect is weaker in recent years. In an attempt to explain the day-of-the-week effect, we demonstrate that short sales do not seem to play a significant role, which is contrary to the findings of Chen and Singal (2003) who study the US stock market. However, stock liquidity (measured by turnover ratio) seems to be related to the day-of-the-week effect in the Taiwan stock market.

This paper demonstrates analytically how short sellers can put non-transitory downward pressure on the stock market prices and intrinsic values of companies that need to raise external capital because of insufficient internal liquidity. The model helps explain anomalous empirical findings in the extant literature on negative returns to stocks subjected to heavy shorting activity. The implications of the model also supply normative justification for the sizable cash reserves held by corporations and their reluctance to raise external capital. The equity pricing effects implied by the model are illustrated for a large empirical sample of companies negatively impacted by heavy short sales. Empirical tests are also conducted in this research that provide evidence consistent with the theory.

This study draws on classical conditioning to explain how investors react to short sale-related measures. Our results reveal that measures related to the capital cost of short sellers cause a conditioned response among investors. This explains how investors actually perceive and relate to short sale-related measures and shows that many measures fail to achieve the expected results. Additionally, the conditioned response to measures related to the capital cost of short sellers reveals investor sentiment about the adjustment of short sale margin requirements.