NBER Working Papers by Yu Yuan

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Working Papers

November 2012Arbitrage Asymmetry and the Idiosyncratic Volatility Puzzle
with Robert F. Stambaugh, Jianfeng Yu: w18560
Short selling, as compared to purchasing, faces greater risks and other potential impediments. This arbitrage asymmetry explains the negative relation between idiosyncratic volatility (IVOL) and average return. The IVOL effect is negative among overpriced stocks but positive among underpriced stocks, with mispricing determined by combining 11 return anomalies. The negative effect is stronger, consistent with asymmetry in risks and other impediments inhibiting arbitrageurs in exploiting overpricing. Aggregating across all stocks therefore yields a negative relation, explaining the IVOL puzzle. Further supporting our explanation is a negative relation over time between the IVOL effect and investor sentiment, especially among overpriced stocks.
July 2012The Long of It: Odds that Investor Sentiment Spuriously Predicts Anomaly Returns
with Robert F. Stambaugh, Jianfeng Yu: w18231
Extremely long odds accompany the chance that spurious-regression bias accounts for investor sentiment's observed role in stock-return anomalies. We replace investor sentiment with a simulated persistent series in regressions reported by Stambaugh, Yu and Yuan (2012), who find higher long-short anomaly profits following high sentiment, due entirely to the short leg. Among 200 million simulated regressors, we find none that support those conclusions as strongly as investor sentiment. The key is consistency across anomalies. Obtaining just the predicted signs for the regression coefficients across the 11 anomalies examined in the above study occurs only once for every 43 simulated regressors.

Published: “The Long of It: Odds That Investor Sentiment Spuriously Predicts Anomaly Returns,” Journal of Financial Economics (2014): 613–619, with Jianfeng Yu and Yu Yuan. citation courtesy of

March 2011The Short of It: Investor Sentiment and Anomalies
with Robert F. Stambaugh, Jianfeng Yu: w16898
This study explores the role of investor sentiment in a broad set of anomalies in cross-sectional stock returns. We consider a setting where the presence of market-wide sentiment is combined with the argument that overpricing should be more prevalent than underpricing, due to short-sale impediments. Long-short strategies that exploit the anomalies exhibit profits consistent with this setting. First, each anomaly is stronger--its long-short strategy is more profitable--following high levels of sentiment. Second, the short leg of each strategy is more profitable following high sentiment. Finally, sentiment exhibits no relation to returns on the long legs of the strategies.

Published: Stambaugh, Robert F. & Yu, Jianfeng & Yuan, Yu, 2012. "The short of it: Investor sentiment and anomalies," Journal of Financial Economics, Elsevier, vol. 104(2), pages 288-302. citation courtesy of

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