Arbitrage Asymmetry and the Idiosyncratic Volatility Puzzle

Buying is easier than shorting for many equity investors. Combining this arbitrage asymmetry with the arbitrage risk represented by idiosyncratic volatility (IVOL) explains the negative relation between IVOL and average return. The IVOL‐return relation is negative among overpriced stocks but positive among underpriced stocks, with mispricing determined by combining 11 return anomalies. Consistent with arbitrage asymmetry, the negative relation among overpriced stocks is stronger, especially for stocks less easily shorted, so the overall IVOL‐return relation is negative. Further supporting our explanation, high investor sentiment weakens the positive relation among underpriced stocks and, especially, strengthens the negative relation among overpriced stocks.     

Failures to Deliver,Short Sale Constraints,and Stock Overvaluation

Studying a large sample of publicly available data on failures to deliver, we find that stocks reaching threshold levels of failures become significantly overvalued. Where short sale constraints are especially binding, we report extreme overpricing and subsequent reversals. These findings support the overvaluation hypothesis, although the mispricing is likely to be difficult to arbitrage because of extreme shorting costs. In addition, threshold stocks with low short interest become more overvalued than threshold stocks with high short interest. This suggests that the level of short interest reflects supply‐side effects when the examination conditions on the difficulty of borrowing shares.     

Which Shorts Are Informed?

We construct a long daily panel of short sales using proprietary NYSE order data. From 2000 to 2004, shorting accounts for more than 12.9% of NYSE volume, suggesting that shorting constraints are not widespread. As a group, these short sellers are well informed. Heavily shorted stocks underperform lightly shorted stocks by a risk‐adjusted average of 1.16% over the following 20 trading days (15.6% annualized). Institutional nonprogram short sales are the most informative; stocks heavily shorted by institutions underperform by 1.43% the next month (19.6% annualized). The results indicate that, on average, short sellers are important contributors to efficient stock prices.     

Costly arbitrage and idiosyncratic risk: Evidence from short sellers

Previous studies have shown that high short interest stocks have low subsequent returns. We test whether the persistence of this effect is due to costs limiting arbitrage. The arbitrage cost that we focus on is idiosyncratic risk which, regardless of the arbitrageur’s level of diversification, deters arbitrage activity. Consistent with costly arbitrage, we find that among high short interest stocks a one standard deviation increase in idiosyncratic risk predicts a more than 1% decline in monthly returns. Moreover, idiosyncratic risk does not predict returns across low short interest stocks, and short interest does not predict low returns across low idiosyncratic risk stocks. Our results are robust to commonly used proxies for both transaction costs and short sale constraints.     

Idiosyncratic risk,costly arbitrage,and the cross-section of stock returns

We test a new cross-sectional relation between expected stock return and idiosyncratic risk implied by the theory of costly arbitrage. If arbitrageurs find it more difficult to correct the mispricing of stocks with high idiosyncratic risk, there should be a positive (negative) relation between expected return and idiosyncratic risk for undervalued (overvalued) stocks. We combine several well-known anomalies to measure stock mispricing and proxy stock idiosyncratic risk using an exponential GARCH model for stock returns. We confirm that average stock returns monotonically increase (decrease) with idiosyncratic risk for undervalued (overvalued) stocks. Overall, our results support the importance of idiosyncratic risk as an arbitrage cost.     

Value at risk,mispricing and expected returns

This study investigates how the relation between value-at-risk (VaR) and expected returns differs under different mispricing statuses. We find that a significantly negative VaR-return relation, defined as the VaR effect, is observed only for overpriced stocks, but not for underpriced stocks. Moreover, VaR has an amplification effect on mispricing, indicating that VaR captures risk that deters arbitrage and thus leads to an increase in mispricing. Our results are robust to alternative VaR definitions, subperiod analysis, different market states, and after controlling for other firm characteristics, well-known risk factors, and those variables that have been shown to have amplifying effects on mispricing. Finally, this study also examines the pricing effect of short sale constraints on the VaR effect under different mispricing statuses. Our findings suggest that the VaR effect observed in overpriced stocks becomes more severe as short sales are more constrained.     

Index arbitrage and the pricing relationship between Australian stock index futures and their underlying shares

This paper examines the mispricing of Australian stock index futures. Exogenous and endogenous price volatility is confirmed to have a positive impact on the mispricing spread, after filtering out predictable time series components. More accurate pricing associated with surprise trading volume in the underlying stocks is consistent with arbitrageurs acting to narrow price disparities relative to the futures market. Ex‐ante interest rate volatility is the primary source of risk faced by arbitrageurs and fluctuations in the transaction cost of opening index arbitrage positions influence the extent to which they drive prices towards theoretical fair values.     

Daily short interest,idiosyncratic risk,and stock returns

This paper examines the relation between short selling and returns and the impact of arbitrage costs on short sellers’ behavior. Using daily UK short selling data, we find that stocks with low short interest levels experience significant positive returns on both an equal- and value-weighted basis. Economic theory predicts that short sellers avoid establishing positions in stocks with high idiosyncratic risk. Our results indicate a negative relation between short interest and returns among high idiosyncratic risk stocks and that short selling activity is mostly concentrated in low idiosyncratic risk stocks where it is less costly to arbitrage fundamental risk.     

Cross section of option returns and idiosyncratic stock volatility

This paper presents a robust new finding that delta-hedged equity option return decreases monotonically with an increase in the idiosyncratic volatility of the underlying stock. This result cannot be explained by standard risk factors. It is distinct from existing anomalies in the stock market or volatility-related option mispricing. It is consistent with market imperfections and constrained financial intermediaries. Dealers charge a higher premium for options on high idiosyncratic volatility stocks due to their higher arbitrage costs. Controlling for limits to arbitrage proxies reduces the strength of the negative relation between delta-hedged option return and idiosyncratic volatility by about 40%.     

Media tone and expected stock returns

We find that media tone reflects firm-level expected returns—firms with low-negative tone stories over a few months earn higher returns in the medium to long term than do firms with high-negative tone stories. The tone premium is driven by consistent outperformance of low-negative stocks, while high-negative stocks do not produce significant abnormal returns. The media tone effect is associated with some common risk factors, among which the size factor plays a consistent and most significant role. The tone effect also reflects differences in firms' idiosyncratic risk, and there is evidence that it is partially related to mispricing and limits to arbitrage.     

State‐Level Business Cycles and Local Return Predictability

This study examines whether local stock returns vary with local business cycles in a predictable manner. We find that U.S. state portfolios earn higher future returns when state‐level unemployment rates are higher and housing collateral ratios are lower. During the 1978 to 2009 period, geography‐based trading strategies earn annualized risk‐adjusted returns of 5%. This abnormal performance reflects time‐varying systematic risks and local‐trading induced mispricing. Consistent with the mispricing explanation, the evidence of predictability is stronger among firms with low visibility and high local ownership. Nonlocal domestic and foreign investors arbitrage away the predictable patterns in local returns in 1 year.     

Do idiosyncratic jumps matter?

We show that idiosyncratic jumps are a key determinant of mean stock returns from both an ex post and ex ante perspective. Ex post, the entire annual average return of a typical stock accrues on the four days on which its price jumps. Ex ante, idiosyncratic jump risk earns a premium: a value-weighted weekly long-short portfolio that buys (sells) stocks with high (low) predicted jump probabilities earns annualized mean returns of 9.4% and four-factor alphas of 8.1%. This strategy’s returns are larger when there are greater limits to arbitrage. These results are consistent with investor aversion to idiosyncratic jump risk.     

In Search of Distress Risk

This paper explores the determinants of corporate failure and the pricing of financially distressed stocks whose failure probability, estimated from a dynamic logit model using accounting and market variables, is high. Since 1981, financially distressed stocks have delivered anomalously low returns. They have lower returns but much higher standard deviations, market betas, and loadings on value and small‐cap risk factors than stocks with low failure risk. These patterns are more pronounced for stocks with possible informational or arbitrage‐related frictions. They are inconsistent with the conjecture that the value and size effects are compensation for the risk of financial distress.     

Comovements between heavily shorted stocks during a market squeeze: Lessons from the GameStop trading frenzy

We examine the comovements between stock prices of different heavily shorted companies during a short-squeeze incident. Using the recent GameStop trading frenzy as a case study, we employ wavelet coherence analyses to determine its link with other frequently shorted stocks. We demonstrate a robust positive association between GameStop prices and the performance of high short interest indices. The bubble behavior driven by retail investor herding transmits between different stocks, even from unrelated sectors. Consequently, a single short-squeeze incident may build up into a potentially broader systemic risk, casting doubt on market integrity and stability.     

Credit ratings and the cross-section of stock returns

Low credit risk firms realize higher returns than high credit risk firms. This is puzzling because investors seem to pay a premium for bearing credit risk. The credit risk effect manifests itself due to the poor performance of low-rated stocks (which account for 4.2% of total market capitalization) during periods of financial distress. Around rating downgrades, low-rated firms experience considerable negative returns amid strong institutional selling, whereas returns do not differ across credit risk groups in stable or improving credit conditions. The evidence for the credit risk effect points towards mispricing generated by retail investors and sustained by illiquidity and short sell constraints.     

Does Academic Research Destroy Stock Return Predictability?

We study the out‐of‐sample and post‐publication return predictability of 97 variables shown to predict cross‐sectional stock returns. Portfolio returns are 26% lower out‐of‐sample and 58% lower post‐publication. The out‐of‐sample decline is an upper bound estimate of data mining effects. We estimate a 32% (58%–26%) lower return from publication‐informed trading. Post‐publication declines are greater for predictors with higher in‐sample returns, and returns are higher for portfolios concentrated in stocks with high idiosyncratic risk and low liquidity. Predictor portfolios exhibit post‐publication increases in correlations with other published‐predictor portfolios. Our findings suggest that investors learn about mispricing from academic publications.     

The good news in short interest

Stocks with relatively high short interest subsequently experience negative abnormal returns, but the effect can be transient and of debatable economic significance. In contrast, relatively heavily traded stocks with low short interest experience both statistically and economically significant positive abnormal returns. These positive returns are often larger (in absolute value) than the negative returns observed for heavily shorted stocks. Thus, the positive information associated with low short interest, which is publicly available, is only slowly incorporated into prices, which raises a broader market efficiency issue. Our results also cast doubt on existing theories of the impact of short sale constraints.     

WHAT'S IN A NAME? A CAUTIONARY TALE OF PROFITABILITY ANOMALIES AND LIMITS TO ARBITRAGE

The recent literature investigating profitability anomalies defines profitability in various ways (i.e., gross, operating, and cash based). We show that limits to arbitrage are associated with returns of gross and cash-based operating profitability anomalies, suggesting mispricing. In contrast, returns from the operating profitability strategy have no relation with barriers to arbitrage and exhibit no evidence of mispricing. Additionally, we show that the differential effects of limited arbitrage-related mispricing of gross and cash-based operating profitability anomalies are attributable to their respective correlations with selling, general, and administrative (SG&A) expense and accruals anomalies. We find that SG&A return predictability, like that of accruals, is related to limits to arbitrage. These findings suggest that investors and researchers should proceed with caution when searching for return predictability by redefining profitability measures.     

Short Sales Constraints and Momentum in Stock Returns

Abstract:   We show that stock characteristics identified by D'Avolio (2002) provide a reliable index of the mostly unobservable short sales constraints. Specifically, we find that this index is positively related to the level of short interest and to short selling costs implied by the disparity in prices in the options and stock markets, and is negatively related to future returns. Using this index, we show that the magnitude of momentum returns for the period 1984 to 2001 is positively related to short sales constraints, and loser stocks rather than winner stocks drive this result. We conclude that short sales constraints are important in preventing arbitrage of momentum in stock returns.     

The CDS‐bond basis

We investigate the cross‐sectional variation in the credit default swap (CDS)‐bond bases and test explanations for the violation of the arbitrage relation between cash bond and CDS contract, which states that the basis should be zero in normal conditions. The evidence is consistent with “limits to arbitrage” theories in that deviations are larger for bonds with higher frictions as measured by trading liquidity, funding cost, counterparty risk, and collateral quality. Surprisingly, we find the basis to be more negative when bond lending fee is higher suggesting that arbitrageurs are unwilling to engage in a negative basis trade when short interest on the bond is high.