Revisiting the ICAPM under the distortion of risk–return tradeoff in short-horizon stock returns

We suggest that the distortion of the positive risk–return relation in the ICAPM is a consequence of trading by informed investors to exploit mispricing. We hypothesize and demonstrate that a non-positive (strongly positive) risk–return relation following positive (negative) market returns is attributed to short-selling (purchasing) of overpriced (underpriced) stocks along with optimistic (pessimistic) expectations conditional on good (bad) market news. We verify this asymmetry in the risk–return relation through the indirect risk–return relation conditional on good (bad) market news. We also find that the attenuation (reinforcement) of the positive risk–return relation is more profound in high- (low-) sentiment periods.     

Short-sale constraints and informational efficiency to private information: A natural experiment

Exploiting a regulatory change in short-sale constraints (Regulation SHO) as a natural experiment, this paper examines the effect of short-sale constraints on informational efficiency of stock prices to private information. I find that short-sellers act as informed traders prior to forthcoming analyst news and trade on negative private information. When short-sale constraints are relaxed for pilot stocks (treatment group), both trading volume and stock price sensitivity increase prior to the analyst announcement for bad news but not for good news, relative to that of nonpilot stocks (control group). The findings are consistent with the Diamond and Verrecchia model that predicts that short-selling increases the speed of adjustment of stock prices to private negative information. In the cross-section, the effect of Reg SHO is stronger in stocks of firms with weak and uncertain information environments (i.e., small firms and firms with high analyst forecast dispersion).     

The Lead-Lag Relation Between Spot and Futures Markets Under Different Short-Selling Regimes

We examine the lead‐lag relation between index futures and the underlying index under three types of short‐selling restrictions on stocks in Hong Kong. Our results indicate that lifting short‐selling restrictions can enhance the informational efficiency of the stock market relative to the index futures. We also investigate the impact of two market characteristics, market conditions and the magnitude of mispricing on the lead‐lag relations under different short‐selling regimes. Our findings suggest that if we remove restrictions, the contemporaneous price relation between the futures and cash markets becomes stronger particularly in the falling market and when the cash market is relatively overpriced.     

卖空交易与市场波动性、流动性研究——基于中国香港证券市场的实证分析

本文利用中国香港证券市场数据实证研究了卖空交易机制与市场流动性和波动性的关系。研究结果表明:卖空交易额变动与市场流动性变动之间并没有长期协整关系,但在短期内卖空交易机制会在一定程度上为市场提供流动性;从长期来看市场流动性变化是卖空交易额变化的原因。卖空交易额变化可以解释市场波动性的变化,卖空交易额增加,则市场波动性也将放大,即在一定程度上卖空交易机制会增加市场的波动性。秩和检验显示:推出卖空机制后会显著提升市场流动性和波动性;启用Up-Tick会显著降低市场流动性和波动性,反之反是;暂停"卖空价规则"对卖空交易额没有显著影响,但可显著提升市场波动性和流动性。     

Information of Unusual Trading Volume

This article investigates the information content of stock unusual trading volume from the aspect of firm fundamental information revealed by both earnings formal announcements and preannouncements. By using the stock market data of China from the second quarter of 2003 to the end of 2015, this article provides evidence that, in general, stocks that experience unusually low trading volume over the week prior to earnings announcements have more unfavorable earnings surprises. However, because of the feature of mandatory pre-disclosure policy in China, this article further finds that the relation between unusually low trading volume and unfavorable earnings surprises only exists in the stocks without earnings preannouncements, because fundamental information is incorporated in the stock prices timely around preannouncements date. In addition, unusually low trading volume signals negative fundamental changes revealed by preannouncements, and this effect is more pronounced among stocks with higher short-selling constraints, but unusually high trading volume is value-irrelevant.     

高管减持如何影响投资者预期?——基于超额融券的经验证据

随着我国融资融券业务逐步扩容,投资者向证券公司融券卖出的卖空交易成为市场消化负面信息的重要机制。本文以高管减持事件窗口期的超额融券量为研究对象,采用事件研究法考察我国企业高管减持所任职公司股票对市场预期的影响。实证结果表明,相比估计期,高管减持窗口期超额融券量显著增长,并且减持比例越高或者减持金额越大,超额融券量越高,表明高管减持显著降低了外部投资者对公司股票的价值预期。进一步研究显示,良好的信息透明度能够显著降低高管减持对超额融券量的正向影响。本文用超额融券量直观地度量投资者预期变化,丰富和发展了高管减持经济后果的研究,对规范我国上市公司高管减持行为及监管部门完善相关监管规定具有启示意义。     

卖空压力抑制经理人私有收益吗？——基于中国放松卖空管制的准自然实验

针对放松卖空管制能否抑制经理人私利问题,本文借助我国融资融券制度逐步推行提供的准自然实验机会,采取双重差分法研究了卖空压力对公司经理人私有收益的影响。研究发现,卖空压力显著抑制了经理人的私有收益,在进行了多项稳健性检验之后,该结论依旧成立。进一步的研究中我们还发现,卖空压力对经理人私有收益的抑制作用在信息透明度高、经理人权力较大、行业竞争激烈的公司中表现得更为明显。本文研究结论表明,作为一种外部治理机制,融资融券业务带来的卖空压力缓解了公司内部的委托代理问题。     

Rise and Fall of the First Financial Futures Market in China： The Case of Chinese Government Bond Futures

This paper studies the rise and fall of the first financial futures market in China. We compare the characteristics in the Chinese Government bond futures market with those in the US T-bond futures market. They differ in market design and structure, market governance, margin requirements, position limits, delivery process, and the way in which the settlement price is calculated. Furthermore, with a unique dataset, we show that prior to maturities of government bond futures, traders began to accumulate significant amounts of long positions for several selected contracts without the intention to offset, forcing short position holders to either purchase deliverable bonds or offset futures at highly inflated prices, causing higher market volatility and price disequilibrium in both spot and futures markets. Arbitrage opportunity arises and the market eventually collapses. The lessons learned from the suspension of the Chinese Government bond futures market offer an invaluable learning experience.     

融券卖空与周末效应——-来自Ａ股市场的经验证据

利用沪深Ａ股数据研究融券卖空与周末效应间的关系,检验了Ｃｈｅｎ＆Ｓｉｇｎａｌ（２００３）的理论假说在Ａ股市场的适用性。研究结果显示：样本研究期间存在显著的周末效应,周五的股票日收益率均值显著高于周一,不过股票日收益率最高均值出现在周三;股票日收益率和股票波动性与融券卖空率负相关,股票日交易量则与融券卖空率正相关,且均在统计上高度显著;混合回归模型回归结果显示基本支持Ｃｈｅｎ＆Ｓｉｇｎａｌ（２００３）的研究假说,分位数回归的结果则更加稳健。     

Are stocks desirable in tax-deferred accounts?

Existing literature suggests that, in order to maximize the tax benefit of retirement accounts, investors should follow a “pecking order” location rule of placing highly taxed assets (e.g., bonds) in a tax-deferred account and lightly taxed assets (e.g., stocks) in a taxable account. Empirical evidence, however, documents that a large number of investors violate this rule. In this paper, we show that such violations can be optimal for risk-averse investors who face portfolio constraints. In particular, while the strategy of placing bonds in the tax-deferred account maximizes the expected level of tax benefit, it may lead to volatile benefits under different realizations of stock returns. By holding a similar portfolio in both accounts, investors can achieve a more balanced growth in the two accounts, minimize the likelihood of violating the constraints in the future and hence “smooth” the volatility of the tax benefit. For some risk-averse investors, this smoothing motive can lead to the observed violation of the pecking order location rule. Our model predicts that such violations are more likely when future tax benefits are more volatile, which can occur, for example, when: (i) the tax rate differential across assets increases over time due either to tax law changes or to tax bracket changes for investors; (ii) asset returns are more volatile; and (iii) investors anticipate large future liquidity needs.