卖空机制能够约束内部人减持吗？——基于融资融券制度的经验证据

本文以我国放松卖空管制为视角,探究其对内部人减持的影响。研究表明,卖空机制能够抑制企业内部人减持行为。机制分析发现,卖空对内部人减持的抑制作用是通过缓解股权高溢价实现的。进一步研究表明,卖空能够抑制大股东、董事以及管理层减持,但对监事减持无影响;卖空能够降低内部人减持的获利程度,并且在内部人减持动机更大时,对内部人减持的抑制作用更强;卖空通过约束内部人减持提升了股票定价效率,还有助于降低内部人增持行为。本文的研究结论丰富了卖空和内部人减持领域的文献,并对政府部门完善制度设计具有启示意义。     

Limit order books and trade informativeness

In the microstructure literature, information asymmetry is an important determinant of market liquidity. The classic setting is that uninformed dedicated liquidity suppliers charge price concessions when incoming market orders are likely to be informationally motivated. In limit order book (LOB) markets, however, this relationship is less clear, as market participants can switch roles, and freely choose to immediately demand or patiently supply liquidity by submitting either market or limit orders. We study the importance of information asymmetry in LOBs based on a recent sample of 30 German Deutscher Aktienindex (DAX) stocks. We find that Hasbrouck's (1991) measure of trade informativeness Granger causes book liquidity, in particular that required to fill large market orders. Picking-off risk due to public news-induced volatility is more important for top-of-the book liquidity supply. In our multivariate analysis, we control for volatility, trading volume, trading intensity and order imbalance to isolate the effect of trade informativeness on book liquidity.     

Do Proprietary Algorithmic Traders Withdraw Liquidity during Market Stress?

We investigate the role of proprietary algorithmic traders in facilitating liquidity in a limit order market. Using order‐level data from the National Stock Exchange of India, we find that proprietary algorithmic traders increase limit order supply following periods of both high short‐term stock‐specific volatility and extreme stock price movement. Even following periods of high marketwide volatility, they do not decrease their supply of liquidity. We define orders from high‐frequency traders as a subclass of orders from proprietary algorithmic traders that are revised in less than three milliseconds. The behavior of high‐frequency trading mimics the behavior of its parent class. This is inconsistent with the theory that fast traders leave the market when stress situations arise, although their limit‐order‐supplying behavior becomes weaker when the increase in short‐term volatility is more informational than transitory. Agency algorithmic traders and nonalgorithmic traders behave opposite to proprietary algorithmic traders by reducing the supply of liquidity during stress situations. The presence of faster traders in the market possibly instills the fear of adverse selection in them. We document that the order imbalance of agency algorithmic traders is positively related to future short‐term returns, whereas the order imbalance of proprietary algorithmic traders is negatively related to future short‐term returns.     

做空机制对我国股市波动性影响的实证分析

我国融资融券业务于2010年3月31日正式启动,而作为一种资本市场机制,做空机 制一直以来都饱受理论界和实务界的争议,做空机制对市场波动的影响尚未达成一致结论。本 文考察了做空机制与市场波动性之间的关系。研究发现：（1）在样本期间内,市场波动与做空 机制之间存在长期的稳定关系;（2）买空交易会在一定程度上增加市场波动,而卖空交易会 在一定程度上降低市场波动,但是二者的影响均有限;（3）综合来看,做空机制并不会引起证 券市场的异常波动,即使市场出现了大幅度的震荡,也不是由于卖空机制本身造成的;（4）本 文认为进一步完善做空机制尤其是卖空交易机制有助于稳定市场。本文结论对于评估做空机 制对市场波动的影响,防范经济冲击风险以及加强市场监管具有重要启示。     

中国A股市场过度波动之谜——基于日个股回报率的实证研究

本文首次基于方差差(Variance Difference)指标对股票回报率过度波动进行量化,并分别运用组合研究和Fama-Macbeth回归的方法,从过度波动与股票回报率之间关系的角度研究了中国A股市场的过度波动现象。基于1995-2010年A股日回报率的实证结果表明,A股市场日回报率波动中存在投资者过度反应导致的过度波动,过度波动带来的额外风险"驱逐"了风险回避的理性投资者,使得股市出现低估。通过每月买入过度波动最大的20%股票,同时卖出过度波动最小的20%股票,能获得显著为正的超额收益,并且该超额收益不能被市场风险所解释。     

INSIDER TRADING EFFECTS ON STOCK RETURNS AROUND OPEN-MARKET STOCK REPURCHASE ANNOUNCEMENTS: AN EMPIRICAL STUDY

In this paper we empirically examine the effects of insider trading activities, the percentage of common shares outstanding authorized for repurchase, and management ownership on stock returns around open-market stock repurchase announcements. The study is conducted on a sample of 204 firms that announced open-market stock repurchases between 1982 and 1990. Results show that insider trading activities during the month that immediately precedes the announcement have a significant effect. While stockholders of firms with insider net selling activities earn positive excess returns, those of firms with insider net buying activities earn larger and more significant excess returns. Insider trading activities during more distant periods do not show any effects on stock returns. Results also indicate that management ownership has a significant positive effect on stock returns, and this effect is more positive when the percentage of common shares outstanding authorized for repurchase is large.     

Managers' Trading Around Stock Repurchases

We analyze personal open market trades by managers around stock repurchases by tender offer. With the exception of Dutch auction offers, managers trade their firm's shares prior to repurchase announcements as though repurchases convey favorable inside information to outsiders. Prior to fixed price repurchase offers that do not follow takeover-related events, managers increase their buying and reduce their selling of their firm's shares. Prior to repurchases that follow takeover-related events, only a decrease in selling is found. No abnormal trading precedes Dutch auction repurchase offers.     

The microstructural foundations of leverage effect and rough volatility

We show that typical behaviors of market participants at the high frequency scale generate leverage effect and rough volatility. To do so, we build a simple microscopic model for the price of an asset based on Hawkes processes. We encode in this model some of the main features of market microstructure in the context of high frequency trading: high degree of endogeneity of market, no-arbitrage property, buying/selling asymmetry and presence of metaorders. We prove that when the first three of these stylized facts are considered within the framework of our microscopic model, it behaves in the long run as a Heston stochastic volatility model, where a leverage effect is generated. Adding the last property enables us to obtain a rough Heston model in the limit, exhibiting both leverage effect and rough volatility. Hence we show that at least part of the foundations of leverage effect and rough volatility can be found in the microstructure of the asset.     

How do individual investors trade?

This paper examines how high-frequency trading decisions of individual investors are influenced by past price changes. Specifically, we address the question as to whether decisions to open or close a position are different when investors already hold a position compared with when they do not. Based on a unique data set from an electronic foreign exchange trading platform, OANDA FXTrade, we find that investors’ future order flow is (significantly) driven by past price movements and that these predictive patterns last up to several hours. This observation clearly shows that for high-frequency trading, investors rely on previous price movements in making future investment decisions. We provide clear evidence that market and limit orders flows are much more predictable if those orders are submitted to close an existing position than if they are used to open one. We interpret this finding as evidence for the existence of a monitoring effect, which has implications for theoretical market microstructure models and behavioral finance phenomena, such as the endowment effect.     

高管交易行为、信息不对称与公司治理

基于沪深股市高管交易行为信息披露,在对高管卖出行为短期市场效应研究基础上,进一步研究高管买入、卖出行为的短期和长期市场效应及其产生根源.结果发现,无论从短期还是长期来看,高管买入行为有显著为正的市场效应,而卖出具有显著为负的市场效应,并且交易量越大、日内交易次数越多,市场效应越强烈.进一步结合公司治理理论发现,终极控股股东控制权与现金流权分离导致更强的买入市场效应,而法制环境抑制了买入市场效应.     

The impact of trading halts on liquidity and price volatility: Evidence from the Australian Stock Exchange

This study examines market behaviour around trading halts associated with information releases on the Australian Stock Exchange, which operates an open electronic limit order book. Using the Lee, Ready and Seguin (1994) pseudo-halt methodology, we find trading halts increase both volume and price volatility. Trading halts also increase bid-ask spreads and reduce market depth at the best-quotes in the immediate post-halt period. The results of this study imply that trading halts impair rather than improve market quality in markets that operate open electronic limit order books.     

Microstructure-based manipulation: Strategic behavior and performance of spoofing traders

We examine how investors strategically spoof the stock market by placing orders with little chance of being executed, but which mislead other traders into thinking there is an imbalance in the order book. Using the complete intraday order and trade data of the Korea Exchange (KRX) in a custom data set identifying individual accounts, we find that investors strategically placed spoofing orders which, given the KRX's order-disclosure rule at the time, created the impression of a substantial order book imbalance, with the intent to manipulate subsequent prices. This manipulation, which made use of specific features of the market microstructure, differs from previously studied forms of manipulation based on information or transactions. Roughly half of the spoofing orders were placed in conjunction with day trading. Stocks targeted for manipulation had higher return volatility, lower market capitalization, lower price level, and lower managerial transparency. We also find that spoofing traders achieved substantial extra profits. The frequency of spoofing orders decreased drastically after the KRX altered its order-disclosure rule.     

Market or limit orders?

In this paper we investigate the problem of optimal order placement of an asset listed on an exchange using both market and limit orders in a simple model of market dynamics. We seek to understand under which settings it is optimal to place limit or market orders. Limit orders typically lower transaction costs but increase the risk of incomplete order execution, whereas market orders typically have higher transaction costs but are guaranteed to be executed. Rather than considering order book dynamics to determine if a limit order is executed we rely on price dynamics for this. We look at implementation shortfall in this setup with market impact of trading and propose a dynamic program to find the optimal placement of both market and limit orders for risk-neutral and risk-averse traders. With this we find a bound on the expected cost of trading and show that a trader who behaves optimally should always expect to pay less to trade less. We then solve the dynamic program numerically and examine optimal order placement strategies. We find that the decision between market and limit orders is sensitive to price volatility, risk aversion, and trading costs.     

The price discovery of day trading activities in futures market

Access to information is necessary for market transparency. However, contrary to trading volume and open interest, information related to day trading activities is rarely available. By incorporating unexplored day trading volume in the literature, this paper demonstrates that both the expected open interest and expected day trading volume are consistently and positively correlated with returns, but that one-lagged day trading volume is negatively correlated with futures returns. Meanwhile, both expected and unexpected day trading volume are negatively correlated with volatility, suggesting that arbitrage activities related to unexpected day trading volume may accelerate the movement of futures prices to a new equilibrium. Moreover, open interest provides liquidity but increases volatility. Finally, we strongly suggest that day trading transaction information be released by futures exchanges to achieve greater transparency.     

The next tick on Nasdaq

The Nasdaq stock market provides information about buying and selling interest in its limit order book. Using a vector autoregressive model of trades and returns, I assess the effect of the entire order book on the next tick. I also determine the influence of individual market makers and electronic networks and find evidence that the identity of market participants can be useful information. Finally, I produce a set of dynamic market price responses to buy and sell orders, and I find that these estimates vary with standard measures of liquidity.     

Does vega-neutral options trading contain information?

This study suggests a novel approach for decomposing net options demands into the options order imbalances with and without volatility risk. By analyzing a high-frequency index futures and options dataset, we examine the information content of (i) the direction-motivated order imbalance induced by a single option type, which is exposed to volatility risk, and (ii) that constructed by both calls and puts, which is vega-neutral. The aggregate options order imbalance does not convey information after controlling for futures market trading. However, the intraday options order imbalance by trading without volatility risk significantly predicts spot index returns, though its longer-horizon forecasting ability is relatively weak because of a possible cross-market hedging effect. The predictive abilities of informed foreigners’ trades and out-of-the-money options trading are prominent. Our empirical results suggest that the vega-neutral options trading conveys additional information distinct from the futures order imbalance.     

The Relationship Among Market-Making Revenue, Payment for Order Flow, and Trading Costs for Market Orders

We study the division of market-making revenue among dealer, broker, and trader. When Knight Securities, a major Nasdaq dealer, interacts with market orders in actively traded stocks during the fourth quarter of 1996, we estimate that its revenue is $0.057 per share. Knight pays brokers at least $0.025 per share (44% of revenue) for orders. To examine whether brokers appear to share these payments with traders, we compare net trading costs (trade price net of commissions) for traders using brokers routing Knight orders with estimated net trading costs for traders using the only discount broker we can determine did not directly receive market-making revenue. We find that the net trading cost of the broker refusing order-flow payments does not dominate the net trading cost of all brokers selling order flow to Knight. This finding suggests that order-flow payments do not unambiguously harm traders and challenges the conclusions of extant studies using only trade prices to assess market quality.     

Short selling,margin trading,and the incorporation of new information into prices

Utilizing daily data on Chinese stocks' short selling and margin trading activities and intraday stock trade and quote data, we find a positive association between the degree of information efficiency of stock prices and the intensity of short selling and margin trading. Short selling (margin buying) escalates during the 5 days immediately before significant negative (positive) information events, which suggests short sellers (margin buyers) anticipate forthcoming news. Using the adverse selection component of the bid–ask spread as a proxy, we find that short selling and margin trading are associated with an improved information environment. Taken together, our empirical evidence supports the conjecture that short selling and margin trading in the Chinese market help stock prices incorporate new information more efficiently. Utilizing the unique Chinese regulation, we also examine the role of brokerages authorized for such trading and document a non-linear relation between pricing efficiency and the number of authorized brokerages.     

Stock markets fragmentation,volatility and final investors

The 2000s in equity markets are marked by two major regulatory shocks: RegNMS in the United States, and MiFID in the European Union. Simultaneously, there is a massive increase in the proportion of high-frequency trading, and market orders volume. However, trading volumes do not significantly increase. We propose a theoretical model describing the effects of stock markets fragmentation on two types of investors optimization problems: “intermediary” high-frequency and “final” investors. Volatility has a permanent and a transitory component, whose weights depend on market fragmentation via the share of non-marketable orders of intermediary investors. The trading volume of final investors depends on market fragmentation both directly via transaction costs, and indirectly via total volatility. Finally a shock in fragmentation may lead to a decrease in trading volume, enhanced in the case of an equity markets crisis by a rise in the components of volatility.     

Is the Electronic Open Limit Order Book Inevitable?

Under fairly general conditions, the article derives the equilibrium price schedule determined by the bids and offers in an open limit order book. The analysis shows: (1) the order book has a small-trade positive bid-ask spread, and limit orders profit from small trades; (2) the electronic exchange provides as much liquidity as possible in extreme situations; (3) the limit order book does not invite competition from third market dealers, while other trading institutions do; (4) If an entering exchange earns nonnegative trading profits, the consolidated price schedule matches the limit order book price schedule.