Robust multivariate portfolio choice with stochastic covariance in the presence of ambiguity

This paper provides the optimal multivariate intertemporal portfolio for an ambiguity averse investor, who has access to stocks and derivative markets, in closed form. The stock prices follow stochastic covariance processes and the investor can have different levels of uncertainty about the diffusion parts of the stocks and the covariance structure. We find strong evidence that the optimal exposures to stock and covariance risks are significantly affected by ambiguity aversion. Welfare analyses show that investors who ignore model uncertainty incur large losses, larger than those suffered under the embedded one-dimensional cases. We further confirm large welfare losses from not trading in derivatives as well as ignoring intertemporal hedging, we study the impact of ambiguity in that regard and justify the importance of including these factors in the scope of portfolio optimization. Conditions are provided for a well-behaved solution in general, together with verification theorems for the incomplete market case.     

Portfolio management with stochastic interest rates and inflation ambiguity

We solve, in closed form, a stock-bond-cash portfolio problem of a risk- and ambiguity-averse investor when interest rates and the inflation rate are stochastic. The expected inflation rate is unobservable, but the investor can learn about it from observing realized inflation and stock and bond prices. The investor is ambiguous about the inflation model and prefers a portfolio strategy which is robust to model misspecification. Ambiguity about the inflation dynamics is shown to affect the optimal portfolio fundamentally different than ambiguity about the price dynamics of traded assets, for example the optimal portfolio weights can be increasing in the degree of ambiguity aversion. In a numerical example, the optimal portfolio is significantly affected by the learning about expected inflation and somewhat affected by ambiguity aversion. The welfare loss from ignoring learning or ambiguity can be considerable.     

中国股债市场长期动态相关性的影响因素研究——基于宏观不确定性和协动性视角

本文借鉴现代宏观经济学中的无套利仿射模型,基于"定价核"的定价方式,将股票市场和债券市场收益率之间的相关系数分解为其主要驱动因素--通货膨胀、真实利率和股息率的不确定性,以及三者之间的协方差。在实证部分,采用DCC-MGARCH模型计算股票市场和债券市场收益率的动态相关系数,验证中国股债相关性的时变规则;进而通过回归分析探究所选取的解释变量对中国股债相关性的贡献。结果表明,通货膨胀和股息率的不确定性以及真实利率与通货膨胀和股息率各自之间的协动性是影响这种相关性的主要因素;通胀冲击、真实利率和股息率可以解释这种相关性与长期动态的暂时背离。其中,通货膨胀和股息率的不确定性对股债相关性的影响与其他欧美主要经济体有着不同的表现,反映了中国市场的特殊性;此外,相较于中国经济市场的平稳时期,股市动荡期间各经济因素的影响会发生改变,且模型解释力会降低。     

Communication and Comovement: Evidence from Online Stock Forums

We study investor communication and stock comovement using a novel data set from an active online stock forum in China. We find substantial comovement among the returns of a stock and its “related stocks,” which are frequently discussed in the subforum dedicated to the given stock. Comovement is greater when the discussion of related stocks is more intensive. Further, the effect of communication on comovement is stronger for stocks associated with higher information uncertainty. Codiscussed stocks are more actively traded and experience more correlated trading. A trading strategy that exploits communication‐driven comovement generates abnormal returns. Our findings highlight the impact of investor communication on asset comovement.     

The lead-lag relation between the stock and the bond markets

I examine the relative informational efficiency of bonds and the underlying stocks through the lead-lag relation between their daily returns. I find that stock returns lead the returns of high yield bonds but not those of investment grade bonds, which indicates that the stock market is relatively more informational efficient than the bond market. The findings imply trading opportunities for the bonds that are highly sensitive to the release of new information. I also find that stocks detect impending defaults earlier than bonds, which implies that bond holders may have enough time to protect their capital.     

Home-field advantage or a matter of ambiguity aversion? Local bias among German individual investors

This paper investigates whether familiarity induced by ambiguity aversion can help explaining the local bias phenomenon among individual investors. Using geographic closeness as a proxy for investor familiarity, we find that investors pull out of (unfamiliar) remote stocks and pour into (familiar) local stocks during times of increased market uncertainty. Moreover, the magnitude of this ‘flight to familiarity’ increases in the spread of an investor's ambiguity (about expected returns) between local and remote stocks. Our results prove robust to a number of alternative explanations of local bias. Specifically, we rule out a ‘home-field advantage’, where investors are able to translate information advantages about nearby companies into excess returns on their local stockholdings. We conclude that individual investors’ local bias is induced by ambiguity aversion in the portfolio selection process rather than a trading strategy based on superior information about local companies.     

Does the Failure of the Expectations Hypothesis Matter for Long‐Term Investors?

We solve the portfolio problem of a long‐run investor when the term structure is Gaussian and when the investor has access to nominal bonds and stock. We apply our method to a three‐factor model that captures the failure of the expectations hypothesis. We extend this model to account for time‐varying expected inflation, and estimate the model with both inflation and term structure data. The estimates imply that the bond portfolio of a long‐run investor looks very different from the portfolio of a mean‐variance optimizer. In particular, time‐varying term premia generate large hedging demands for long‐term bonds.     

Is the disposition effect in bonds as strong as in stocks? Evidence from an emerging market

Does the disposition effect appear in bond trades as in stocks? We apply Odean's measurement (1998) to a proprietary transaction database with unique investor IDs from an emerging market exchange that holds both stock and bond trading. We find some disposition effect in treasury bonds, but much lower than in stocks, and a positive relation between the two measures by investor. In addition, we find a significant disposition effect for local individuals and family offices, in both markets. In contrast, long-term institutions, brokerage firms, and foreign investors do not exhibit this bias. This is the first study to report evidence of the disposition effect in a fixed-income market.     

The effects of dividend yield and dividend policy on common stock prices and returns

This paper suggests that it is not possible to demonstrate, using the best available empirical methods, that the expected returns on high yield common stocks differ from the expected returns on low yield common stocks either before or after taxes. A taxable investor who concentrates his portfolio in low yield securities cannot tell from the data whether he is increasing or decreasing his expected after-tax return by so doing. A tax exempt investor who concentrates his portfolio in high yield securities cannot tell from the data whether he is increasing or decreasing his expected return. We argue that the best method for testing the effects of dividend policy on stock prices is to test the effects of dividend yield on stock returns. Thus the fact that we cannot tell, using the best available methods, what effects dividend yield has on stock returns implies that we cannot tell what effect, if any, a change in dividend policy will have on a corporation's stock price.     

Does the source of uncertainty matter? The impact of financial,newspaper and Twitter-based measures on U.S. banks

This study examines if the source of uncertainty (newspaper, Twitter, financial market) matters in its impact on bank stock returns in the United States. By applying discrete wavelet transformation, we model directional spillovers and Granger causality between uncertainty and bank returns for different time horizons. Our results demonstrate that this distinction between time horizons is crucial. Although newspaper and Twitter-based measures are correlated, they capture a different source of investor perception. Twitter-based uncertainty adversely affects bank stocks in the short run, while newspaper-based policy uncertainty is relevant in the medium run. Financial-based uncertainty, VIX, is the most important factor. Moreover, we find that the impact of uncertainty on bank returns is stronger during the COVID-19 pandemic and for banks with a high ratio of loans to total assets and large off-balance-sheet activities.     

Investing for the Long Run when Returns Are Predictable

We examine how the evidence of predictability in asset returns affects optimal portfolio choice for investors with long horizons. Particular attention is paid to estimation risk, or uncertainty about the true values of model parameters. We find that even after incorporating parameter uncertainty, there is enough predictability in returns to make investors allocate substantially more to stocks, the longer their horizon. Moreover, the weak statistical significance of the evidence for predictability makes it important to take estimation risk into account; a long-horizon investor who ignores it may overallocate to stocks by a sizeable amount.     

Ambiguity and risk factors in bank stocks

The determinants of banks' cost of equity are not well understood. We depart from prior work assuming rational expectations and instead explore the impact of Knightian uncertainty or ambiguity on bank stocks. We test a large set of asset pricing models and find that investors' lack of confidence in both the drift and correlation structure driving bank stock returns affects banks' cost of capital. We also investigate the economic relation among ambiguity, market liquidity, and banks' capital shortfall, which reveals the transmission channels through which ambiguity may increase the probability of a systemic crisis. Our findings have implications for macroprudential policy.     

The Variation of Economic Risk Premiums in Real Estate Returns

We examine the predictable components of returns on stocks, bonds, and real estate investment trusts (REITs). We employ a multiple-beta asset pricing model and find that there are varying degrees of predictability among stocks, bonds, and REITs. Furthermore, we find that most of the predictability of returns is associated with the economic variables employed in the asset pricing model. The stock market risk premium is highly important in capturing the predictable variation in stock portfolios, and the bond market risk premiums (term and risk structure of interest rates) are important in capturing the predictable variation in bond portfolios. For REITs, however, both the stock and bond market risk premiums capture the predictable variation in returns. REITs have comparable return predictability to stock portfolios. We conclude that there is an important economic risk premium for REITs that are not captured by traditional multiple-beta asset pricing models.     

Political uncertainty and risk premia

We develop a general equilibrium model of government policy choice in which stock prices respond to political news. The model implies that political uncertainty commands a risk premium whose magnitude is larger in weaker economic conditions. Political uncertainty reduces the value of the implicit put protection that the government provides to the market. It also makes stocks more volatile and more correlated, especially when the economy is weak. We find empirical evidence consistent with these predictions.     

Institutional investor’ proportions and inactive trading

We focus on a typical market anomaly-inactive trading: trading volume shrinks while stock price abnormally jumps. We calibrate a theoretical model with variance ambiguity heterogeneous among investors and illustrate that ambiguity averse investors' proportions enhance trading volume shrinkage and abnormal price jumps. We provide a cross-section analysis of stocks' inactive trading by introducing institutional investors' proportions to measure investor structures' differences among stocks. We also empirically measure relative inactive trading for constituent stocks in S&P 500 from 2014 to 2019 and demonstrate that institutional investors' proportion is negatively related to inactive trading. Finally, we demonstrate that higher proportions of institutional investors lead to less inactive trading anomalies.     

Model Misspecification and Underdiversification

In this paper, we study intertemporal portfolio choice when an investor accounts explicitly for model misspecification. We develop a framework that allows for ambiguity about not just the joint distribution of returns for all stocks in the portfolio, but also for different levels of ambiguity for the marginal distribution of returns for any subset of these stocks. We find that when the overall ambiguity about the joint distribution of returns is high, then small differences in ambiguity for the marginal return distribution will result in a portfolio that is significantly underdiversified relative to the standard mean‐variance portfolio.     

Who Owns What? A Factor Model for Direct Stockholding

We build a cross-sectional factor model for investors' direct stockholdings and estimate it using data from almost 10 million retail accounts in the Indian stock market. Our model identifies strong investor clienteles for stock characteristics, most notably firm age and share price, and for particular clusters of stock characteristics. These clienteles are intuitively associated with investor attributes such as account age, size, and diversification. Coheld stocks tend to have higher return covariance, inconsistent with simple models of diversification but suggestive that clientele demands influence stock returns.     

Investment Horizon and Repo in the Over‐the‐Counter Market

This paper presents a three‐period model featuring a short‐term investor in the over‐the‐counter bond market. A short‐term investor stores cash because of a need to pay cash at some future date. If a short‐term investor buys bonds, then a deadline for retrieving cash lowers the resale price of bonds for the investor through bilateral bargaining in the bond market. Ex‐ante, this hold‐up problem explains the use of a repo by a short‐term investor, the existence of a haircut, and the vulnerability of a repo market to counterparty risk. This result holds without any uncertainty about bond returns or asymmetric information.     

Investor sentiment,flight-to-quality,and corporate bond comovement

We examine the dynamics of bond correlation using a broad sample of US corporate bonds, and document that bond correlation varies heavily over time. We attribute this variation in bond correlation to variation in risk factor correlation reflecting time-varying flight-to-quality behavior of investors. We show that risk factor correlation increases when investor sentiment worsens, i.e., corporate bond investors exhibit stronger flight-to-quality when their sentiment is bad. Thus, bad investor sentiment leads to flight-to-quality behavior and, ultimately, high bond correlation. Very good sentiment, in contrast, can cause risk factor correlation and bond correlation to be negative.