换月效应、窗饰与股指期货合约到期日设计

本文以上证指数为研究对象．对股票市场换月效应与月末效应进行研究后发现，指数在月末最后一个交易日收益率波动率显著大于月平均收益率波动率，上证指数收益率存在显著的换月效应。这种现象可能与基金的窗饰效应有关。为了防止期货到期日效应与现货月效应及假日效应等重叠，增大现货市场的波动性，本文建议将股指期货合约最后交易日设在月中。     

DAY‐END EFFECT ON THE PARIS BOURSE

We study the day‐end effect on the Paris Bourse, a computerized order‐driven market with competing dealers. The day‐end return is approximately double the magnitude found in U.S. data and is nearly four times larger for stocks trading with a registered dealer. However, this is largely explained by the time between trades and the bid‐ask spread. Unlike the U.S. data, the effect does not decline as stock price increases, probably because of a variable tick size in the Paris market. Finally, a change to a closing call auction in May 1996 for a subset of stocks did not reduce the day‐end effect.     

THE FUNDAMENTAL DETERMINANTS OF TRADING VOLUME REACTION TO FINANCIAL INFORMATION: EVIDENCE AND IMPLICATIONS FOR EMPIRICAL CAPITAL MARKET RESEARCH

Prior empirical research indicates that trading volume reaction to new information increases with the heterogeneity of investors’ prior beliefs. We examine three potential factors that theoretical models of financial economists show determine trading volume reaction to new information: heterogeneous prior beliefs, differential interpretation, and the consensus effect—the extent to which the information causes their beliefs to converge or diverge. We find that these three factors have a distinct and significant incremental effect on trading volume, thereby suggesting that empirical trading volume models that exclude or fail to control for any of these determinants are misspecified with biased estimated coefficients.     

Affirmative obligations and market making with inventory

Existing empirical studies provide little support for the theoretical prediction that market makers rebalance their inventory through revisions of quoted prices. This study provides evidence that the NYSE's specialist does engage in significant inventory rebalancing, but only when not constrained by the affirmative obligation to provide liquidity imposed by the Price Continuity rule. The evidence also suggests that such obligations are associated with better market quality, but impose significant costs on the specialist. The specialist mitigates these costs through discretionary trading when the rule is not binding. These findings shed light on how exchange rules affect market makers’ behavior and market quality.     

The persistent effects of a false news shock

In September 2008, a six-year-old article about the 2002 bankruptcy of United Airlines' parent company resurfaced on the Internet and was mistakenly believed to be reporting a new bankruptcy filing by the company. This episode caused the company's stock price to drop by as much as 76% in just a few minutes, before NASDAQ halted trading. After the “news” had been identified as false, the stock price rebounded, but still ended the day 11.2% below the previous close. We explore this natural experiment by using a simple asset-pricing model to study the aftermath of this false news shock. We find that, after three trading sessions, the company's stock was still trading below the two-standard-deviation band implied by the model and that it returned to within one standard deviation only during the sixth trading session. On the seventh day after the episode, the stock was trading at the level predicted by the asset-pricing model. We investigate several potential explanations for this finding, but fail to find empirical evidence supporting any of them. We also document that the false news shock had a persistent negative effect on the stock prices of other major airline companies. This is consistent with the view that contagion effects would have dominated competitive effects had the bankruptcy actually taken place.     

VOLATILITY FORECASTS,TRADING VOLUME,AND THE ARCH VERSUS OPTION‐IMPLIED VOLATILITY TRADE‐OFF

We investigate empirically the role of trading volume (1) in predicting the relative informativeness of volatility forecasts produced by autoregressive conditional heteroskedasticity (ARCH) models versus the volatility forecasts derived from option prices, and (2) in improving volatility forecasts produced by ARCH and option models and combinations of models. Daily and monthly data are explored. We find that if trading volume was low during period t?1 relative to the recent past, ARCH is at least as important as options for forecasting future stock market volatility. Conversely, if volume was high during period t?1 relative to the recent past, option‐implied volatility is much more important than ARCH for forecasting future volatility. Considering relative trading volume as a proxy for changes in the set of information available to investors, our findings reveal an important switching role for trading volume between a volatility forecast that reflects relatively stale information (the historical ARCH estimate) and the option‐implied forward‐looking estimate.     

Volatility and dark trading: Evidence from the Covid-19 pandemic

We study the effect(s) of volatility on the share of trading in dark pools by exploiting the exogenous shock of the Covid-19 pandemic on financial markets and regulatory restrictions on dark trading. We find that high levels of volatility in lit exchanges is linked to an economically significant loss of market share by dark pools to lit exchanges. In line with the theory, the loss appears to be driven by informed traders’ migration from lit to dark markets during high volatility periods. The market quality implications of the trading dynamics are mixed: while it tempers liquidity decline in the lit market, it exacerbates the loss of informational efficiency.     

Overreaction of country ETFs to US market returns: Intraday vs. daily horizons and the role of synchronized trading

In this paper we study the intraday price formation process of country Exchange Traded Funds (ETFs). We identify specific parts of the US trading day during which Net Asset Values (NAVs), currency rates, premiums and discounts, and the S&P 500 index have special effects on ETF prices, and characterize a special intraday and overnight updating structure between these variables and country ETF prices. Our findings suggest a structural difference between synchronized and non-synchronized trading hours. While during synchronized trading hours ETF prices are mostly driven by their NAV returns, during non-synchronized trading hours the S&P 500 index has a dominant effect. This effect also exceeds the one that the S&P 500 index has on the underlying foreign indices and suggests an overreaction to US market returns when foreign markets are closed.     

The pricing and performance of leveraged exchange-traded funds

Leveraged ETFs are a recent and very successful financial innovation. They provide daily returns that are in a multiple or a negative multiple of the daily returns on a market benchmark. In this paper, we examine the characteristics, trading statistics, pricing efficiency and tracking errors of a sample of leveraged ETFs. We find that these ETFs are traded mainly by retail traders with very short holding periods. Price deviations (from NAV) are small on average, but large premiums and discounts are prone to occur. More interestingly, the behavior of premiums is different between bull (i.e., those with a positive multiple) and bear ETFs (i.e., those with a negative multiple). Our findings are consistent with the argument that the end-of-day rebalancing of the funds’ exposures increases market volatility at the close of a trading day. As for tracking errors, they are small for holding periods of up to a week, but become increasingly larger for longer horizons.     

Derivatives traders’ reaction to mispricing in the underlying equity

This article examines trading behavior in the options market conditioned on mispricing in the underlying stock. We investigate the price equilibrium between the observed equity asset and the options-implied synthetic share as well as the relative divergence between the two prices. We find a consistently positive relation between the level of stock mispricing and violations of the upper-boundary condition using derivatives, along with an increase in price divergence. To control for the effect of shorting limitations on mispricing, we further examine prices during the short-sale ban in 2008. The results hold and in many instances are more significant during the ban period. Given the persistent disequilibria between the synthetic and observed stock prices, we argue the results are evidence of informed trading in the derivatives market.     

Performance Evaluation Of U.K. Unit Trusts Within The Stochastic Discount Factor Framework

We examine the performance of U.K. unit trusts between January 1982 and December 1996 within the stochastic discount factor approach across a wide class of models. No one model dominates the others in correctly pricing passive portfolios or detecting superior performance for hypothetical trading strategies. We find no evidence of significant superior performance by the unit trusts for any model of the stochastic discount factor. Also, the charges of the trust have a mixed effect on trust performance.     

Do Hedge Funds Manipulate Stock Prices?

We provide evidence suggesting that some hedge funds manipulate stock prices on critical reporting dates. Stocks in the top quartile of hedge fund holdings exhibit abnormal returns of 0.30% on the last day of the quarter and a reversal of 0.25% on the following day. A significant part of the return is earned during the last minutes of trading. Analysis of intraday volume and order imbalance provides further evidence consistent with manipulation. These patterns are stronger for funds that have higher incentives to improve their ranking relative to their peers.     

Do option markets undo restrictions on short sales? Evidence from the 2008 short-sale ban

The effectiveness of any sanction depends on the costs of avoiding its restrictions. We examine whether bearish option strategies were substitutes for short sales during the September 2008 short-sale ban. We find a significant diminution in option volumes and a significant increase in option bid-ask spreads for banned stock relative to unbanned stock during the ban period. Apparent violations of the put-call parity bound became significantly more frequent for banned stocks during the ban period. We conclude that the ban acted as an effective restriction on trading in options.     

The S&P500 index effect reconsidered: Evidence from overnight and intraday stock price performance and volume

This study focuses on S&P500 inclusions and deletions, examining the impact of potential overnight price adjustment after the announcement of an S&P500 index change. We find evidence of a significant overnight price change that diminishes the returns available to speculators although there are still profits available from the first day after announcement until a few days after the actual event. More importantly, observing the tick-by-tick stock price performance and volume effects on the key days during the event window for the first time, we find evidence of consistent trading patterns during trading hours. A separate analysis of NASDAQ and NYSE listed stocks allows for a detailed examination of the price and volume effect at an intra-day level. We find that index funds appear to cluster their rebalancing activities near to and after the close on the event date, suggesting that they are more concerned with tracking error than profit.     

ROBUSTNESS OF THE HEADQUARTERS‐CITY EFFECT ON STOCK RETURNS

Recent studies report that U.S. firms headquartered near each other experience positive comovement in their stock returns, a finding suggestive of local biases in equity trading activity. We investigate the robustness of these findings and find that including additional pricing factors in models for monthly stock returns materially reduces the magnitude of the headquarters‐city effect in stock returns. Additionally, we find that an implicit null hypothesis of zero local return comovement is inappropriate as there is positive comovement between a stock's return and returns on portfolios of stocks from nonheadquarters cities, on average. Nevertheless, results benchmarked against estimates based on resampling methods indicate a significant and robust headquarters‐city effect in stock returns.     

WHAT'S IN A NICKNAME? PRICE AND VOLUME EFFECTS OF A PURE TICKER SYMBOL CHANGE

We examine the effect of a voluntary change in ticker symbol without other contemporaneous corporate events such as a name change. We find significant declines in trading volume and prices on the effective date of the ticker change. We segment the sample by exchange listing, share turnover activity, and subperiod. We observe declines in trading volume in all subsamples and negative abnormal returns in recent years.     

Informed trading,information uncertainty,and price momentum

In this paper we investigate the effects of informed trading (PIN) and information uncertainty in determining price momentum. We find that trading strategies based on buying high-uncertainty good-news stocks and shorting high-uncertainty bad-news stocks work well when limited to high-PIN stocks, while stocks with low-PIN do not exhibit price continuations, even when the uncertainty level of those stocks is high. In contrast, momentum returns are always significant for high-PIN stocks, irrespective of information uncertainty. Overall, we show that the informed trading effect is both independent of and stronger than that of information uncertainty in determining price momentum.     

Competition between Exchanges: Euronext versus Xetra

Exchanges in Europe are in a process of consolidation. After the failure of the proposed merger between Deutsche Börse and Euronext, these two groups are likely to become the nuclei for further mergers and co‐operation with currently independent exchanges. A decision for one of the groups entails a decision for the respective trading platform. Against that background we evaluate the attractiveness of the two dominant continental European trading systems. Though both are anonymous electronic limit order books, there are important differences in the trading protocols. We use a matched‐sample approach to compare execution costs in Euronext Paris and Xetra. We find that both quoted and effective spreads are lower in Xetra. The differences are more pronounced for less liquid stocks. When decomposing the spread we find no systematic differences in the adverse selection component. Realised spreads, on the other hand, are significantly higher in Euronext. Neither differences in the number of liquidity provision agreements nor differences in the minimum tick size or in the degree of domestic competition for order flow explain the different spread levels. We thus conclude that Xetra is the more efficient trading system.     

Conflicts of interest and China's A-share underpricing

The extremely high A-share underpricing in China's primary market provides us with a very interesting area of empirical research. Previous studies on China's IPO underpricing have been suggestive, but inconclusive. A significant decline in A-share underpricing is found in 2003 relative to previous years (and much less than that recorded in the literature to date). We examine the validity of previous A-share underpricing models, reported in the literature, and find a statistically significant structural break in the data during 2003 when these models are specified. We further explore conflicts of interest in the Chinese IPO market and specify an alternative model to further examine this change in observed market behavior. Our results suggest that a contract with high underwriter's fee leads to less A-share underpricing. Our results also suggest that the asymmetric information hypothesis does not apply in the Chinese IPO market in 2003. Overpricing by the secondary market and the trading activity on the first trading day are the main functions of the A-share underpricing. This study has important implications such as guiding the Chinese government policy regarding the regulations of initial public offering.     

Short sellers and insider trading profitability: A natural experiment

We examine the impact of short sellers on insider trading profitability using a natural experiment of a pilot program which relaxed short-selling constraints for randomly selected pilot stocks. We find that pilot firms experienced a significant decrease in insider trading profitability during the pilot program. The results are more pronounced for the pilot firms with poor information quality, and for the pilot firms without corporate restrictions on insider trading. Our evidence suggests that short sellers serve an important market disciplinary role by reducing insider trading profitability.