Downward-Sloping Demand Curves, the Supply of Shares, and the Collapse of Internet Stock Prices

Over March and April 2000, Internet stocks lost 56%, or $700 billion. This sudden collapse has been attributed to an increasing supply of shares from lockup expirations and equity offerings. I show that Internet stocks collapsed in this period regardless of whether their lockups expired. Furthermore, daily Internet stock portfolio returns were almost unaffected by the number or dollar amount of lockup expirations that day, or by the amount of stock offered in IPOs or SEOs. Most of the Internet stock decline is explained by poor marketwide returns, particularly for growth stocks.     

Options and the Bubble

Many believe that a bubble existed in Internet stocks in the 1999 to 2000 period, and that short‐sale restrictions prevented rational investors from driving Internet stock prices to reasonable levels. In the presence of such short‐sale constraints, option and stock prices could decouple during a bubble. Using intraday options data from the peak of the Internet bubble, we find almost no evidence that synthetic stock prices diverged from actual stock prices. We also show that the general public could cheaply short synthetically using options. In summary, we find no evidence that short‐sale restrictions affected Internet stock prices.     

Interaction Between Short Selling and Potential Insider Selling in the IPO Aftermarket

We document the determinants of short interest in newly public firms during the lockup period and how short interest influences the valuation effects surrounding lockup expiration. We find that the short interest is larger for stocks that have more downward price potential at lockup expiration. We also find that the stocks that are subjected to larger short positions experience more pronounced negative valuation effects upon lockup expiration. Finally, we find that the stocks with a larger short interest position just after lockup expiration experience weaker returns during the following the six-month period.     

Short-sale constraints and the idiosyncratic volatility puzzle: An event study approach

Using three natural experiments, we test the hypothesis that investor overconfidence produces overpricing of high idiosyncratic volatility stocks in the presence of binding short-sale constraints. We study three events: IPO lockup expirations, option introductions, and the 2008 short-sale ban on financial firms. Consistent with our prediction, we show that when short-sale constraints are relaxed, event stocks with high idiosyncratic volatility tend to experience greater price reductions, as well as larger increases in trading volume and short interest, than those with low idiosyncratic volatility. These results hold when we benchmark event stocks with non-event stocks with comparable idiosyncratic volatility. Overall, our findings suggest that biased investor beliefs and binding short-sale constraints contribute to idiosyncratic volatility overpricing.     

首日涨停板制度与IPO解禁效应——基于投机泡沫视角的分析

本文以2006—2016年上市的1397家公司为研究样本,实证检验了首日涨停板制度对新股解禁效应的影响。结果发现:首日涨停板制度实施期间发行的新股,解禁时有显著更差的市场表现,[-30,30]窗口期间的超额回报低至-8.43%,同时有更小的异常交易量和异常波动率;新股上市时股价高估程度越大、投资者情绪越高,首日涨停板制度对解禁效应的影响越强。上述结果支持了Hong et al.(2006)提出的“解禁与资产泡沫破灭”的理论,即首日涨停板制度导致新股发行后投机泡沫累积,投机泡沫破灭导致解禁时更大幅度的股价下跌。本文的研究结论补充了首日涨停板制度后果的文献,并对防范金融风险和完善新股市场化改革具有一定的政策参考价值。     

Effect of the ban on short selling on market prices and volatility

We examine the effects of the short‐selling ban, imposed by Australian regulators in the wake of the global financial crisis, on the trading of financial stocks. Our findings argue against commonly stated reasons for imposing short‐sale bans. We find no evidence that short‐sale restrictions provide support for stock prices or that they reduce volatility. Moreover, stocks subject to the short‐selling ban suffered a severe degradation in market quality. Controlling for the adverse effects of the financial crisis on markets, we show that short‐selling restrictions increase intraday volatility, reduce trading activity and increase bid–ask spreads.     

Regulatory Uncertainty and Market Liquidity: The 2008 Short Sale Ban's Impact on Equity Option Markets

We examine how the September 2008 short sale restrictions and the accompanying confusion and regulatory uncertainty impacted equity option markets. We find that the short sale ban is associated with dramatically increased bid‐ask spreads for options on banned stocks. In addition, synthetic share prices for banned stocks become significantly lower than actual share prices during the ban. We find similar results for synthetic share prices of hard‐to‐borrow stocks, suggesting that the dislocation in actual and synthetic share prices is attributable to the increased hedging costs for options on banned stocks during the short sale ban.     

Distribution of Ownership,Short Sale Constraints,and Market Efficiency: Evidence from Cross‐Listed Stocks

We investigate the interplay between the distribution of ownership, short sale constraints, and market efficiency. Using minute‐by‐minute data during the period surrounding the short sale ban of 2008, we demonstrate that short sale restrictions cause price disparities among cross‐listed stocks when ownership in the stocks is distributed unevenly across the two markets. The stocks tend to trade at a premium in the market where long sellers are relatively scarcer, which reduces the speed at which prices adjust to bad news. The premium is driven primarily by an increase on the ask side of the market where ownership is thinner, is only evident when prices are moving down, and disappears quickly.     

Can Short Restrictions Actually Increase Informed Short Selling?

We use the 2008 short selling regulations to test whether short sale restrictions can increase informed short selling. For the preborrow requirement, we find more negative price reactions to short interest announcements though no reliable increase in the price impact of short sales volume. For the stocks with banned short sales, we find an increase in the price impact of short sale volume though no reliable change in the price reaction to short interest announcements. Both restrictions, however, are associated with increased informed trading. Our results suggest that short restrictions will not reduce informed short selling and may actually result in an increase by increasing the proportion of informed short sellers..     

The skinny on the 2008 naked short-sale restrictions

On July 15, 2008, the US Securities and Exchange Commission announced temporary restrictions on naked short sales of the stocks of 19 financial firms. The restrictions offer a unique empirical setting to test Miller’s (1977) conjecture that short-sale constraints result in overpriced securities and low subsequent returns. Consistent with Miller’s overpricing hypothesis, we find evidence of a positive (negative) market reaction to the announcement (expiration) of the short-sale restrictions. Announcement returns are higher for firms that appear to be subject to more naked short selling in the days immediately preceding the announcement of the restrictions. The restrictions are successful in eliminating naked short sales for the restricted stocks, but naked short sales increase dramatically for a closely matched sample of financial firms during the restricted period. We also find that the restrictions negatively impact various measures of liquidity, including bid-ask spreads and trading volume. From a public policy perspective, our findings suggest that, at a minimum, policymakers should pause when considering further short sale restrictions.     

Asset Float and Speculative Bubbles

We model the relationship between asset float (tradeable shares) and speculative bubbles. Investors with heterogeneous beliefs and short‐sales constraints trade a stock with limited float because of insider lockups. A bubble arises as price overweighs optimists' beliefs and investors anticipate the option to resell to those with even higher valuations. The bubble's size depends on float as investors anticipate an increase in float with lockup expirations and speculate over the degree of insider selling. Consistent with the internet experience, the bubble, turnover, and volatility decrease with float and prices drop on the lockup expiration date.     

Spanning with Short-Selling Restrictions

In principle, the set of attainable payoff vectors is reduced if assets cannot be sold short. However, we show that the original space of payoff vectors is spanned despite short sale restrictions if there is one additional asset whose payoff is a positively weighted sum of the payoffs of the original assets. For example, this condition is automatically fulfilled if the original assets are stocks and the additional asset is an index future consisting of these stocks.     

Why Do Insiders Sell Shares Following IPO Lockups?

We examine long run returns subsequent to the lockup expiration of firms having gone public. We find that returns are negatively associated with abnormal selling by senior executives but unrelated to selling by other insiders. Our results suggest that even though lockup expirations provide an initial opportunity for insiders to diversify their holdings by selling a firm's shares, sales by senior executives are still motivated in part by private information. Sales by other insiders, on the other hand, are consistent with portfolio diversification.     

Earnings Announcements,Differences of Opinion and Management Guidance

Berkman, Dimitrov, Jain, Koch, and Tice (2009) document a negative relationship between differences of opinion and earnings announcement returns, and this relationship is more pronounced when short‐sale constraints are likely to be high. These findings are interpreted as support for the theory in Miller (1977) that binding short sale constraints cause pessimists to be underrepresented in price formation. We conjecture that accounting information (i.e., earnings news) is likely to play a role in this returns pattern. After controlling for the level of earnings news, we find that the relationship between differences of opinion and stock returns is either eliminated or opposite from what is predicted by Miller's theory. Further, we present evidence that suggests the confounding effect of earnings news can be explained by (pessimistic) management earnings guidance. Our findings offer an alternative explanation for why low differences of opinion stocks earn greater abnormal returns around earnings announcements.     

Information Discovery in Share Lockups: Evidence from the Split‐Share Structure Reform in China

We document a prominent abnormal stock return of –14% during the [–120, +20] day window around 482 lockup expirations in the split‐share structure reform in China. The abnormal stock returns (selling volumes) are positively (negatively) correlated with firm information transparency and postreform performance improvement, but negatively (positively) related to the level of agency problems, suggesting the existence of information‐based trading during the lockups. We present important evidence that institutional investors, especially mutual funds, possess superior information discovering capabilities than that of individual investors. Our findings confirm the information roles of lockups as a tool to signal firm quality and a commitment device to alleviate agency problems.     

VENTURE CAPITAL AND IPO LOCKUP EXPIRATION: AN EMPIRICAL ANALYSIS

Most initial public offerings (IPOs) feature “lockup” agreements, which bar insiders from selling the stock for a set period following the IPO, usually 180 days. We examine stock price behavior in the period surrounding lockup expiration for a sample of 2,529 firms from 1988 to 1997. We find that lockup expirations are, on average, associated with significant and negative abnormal returns, but the losses are concentrated in firms with venture capital backing. For the venture‐capital‐backed group, the largest losses occur for high‐tech firms and firms with the greatest post‐IPO stock price increases, the largest relative trading volume in the period surrounding expiration, and the highest quality underwriters. JEL classification: G14, G24     

Changing the rules again: Short selling in connection with public equity offers

We study the impact of two recent regulations that impose restrictions on short selling. First, since October 2007 any investor that short sells a firm’s stock is prohibited from purchasing shares in the firm’s seasoned equity offering (SEO) if the short occurred in the five days prior to the offering (pursuant to an amendment to Rule 105). Previously Rule 105 only disallowed investors from covering a pre-issue short sale with shares purchased in the offering. We hypothesize that the amended rule has the unintended consequence of greater discounting for overnight offers, which are not announced in advance, because the rule excludes some potential buyers and thereby forces underwriters to set lower offer prices to fully distribute the offer. The evidence supports this hypothesis. Second, we examine the impact of the SEC’s 2008 Emergency Order that greatly curtails naked short selling on all stocks under its jurisdiction. We find that the Emergency Order is associated with large increases in discounting for offers announced in advance, suggesting that the removal of naked short sellers is associated with reduced pre-SEO pricing efficiency. Taken together, the results imply that recent restrictions on short selling have significant unintended effects on the capital raising process.     

Costly arbitrage and idiosyncratic risk: Evidence from short sellers

Previous studies have shown that high short interest stocks have low subsequent returns. We test whether the persistence of this effect is due to costs limiting arbitrage. The arbitrage cost that we focus on is idiosyncratic risk which, regardless of the arbitrageur’s level of diversification, deters arbitrage activity. Consistent with costly arbitrage, we find that among high short interest stocks a one standard deviation increase in idiosyncratic risk predicts a more than 1% decline in monthly returns. Moreover, idiosyncratic risk does not predict returns across low short interest stocks, and short interest does not predict low returns across low idiosyncratic risk stocks. Our results are robust to commonly used proxies for both transaction costs and short sale constraints.     

Pursuing Value Through Liquidity in IPOs: Underpricing,Share Retention,Lockup, and Trading Volume Relationships

We argue that in an initial public offering (IPO), pre-IPO owners make decisions regarding underpricing, share retention, and share lockup simultaneously and optimally to maximize aftermarket liquidity. We predict that underpricing fosters higher trading volume in both the short run and the long run. Also, liquidity is negatively related to the proportion of shares retained by pre-IPO owners, ceteris paribus, so IPO underpricing should be positively related to the proportion of shares retained, as an offset. We document evidence consistent with these predictions. In addition, we find that, for IPOs with a lockup restriction, underpricing is more substantial and the positive relation between share retention and underpricing is much stronger. We also find that the relationship between underpricing and trading volume is stronger for IPOs with lockup. IPOs with lockup have higher trading volume, and a significant portion of this difference is associated with the effect of underpricing.JEL Classification: G10, G14, G24     

Failures to Deliver,Short Sale Constraints,and Stock Overvaluation

Studying a large sample of publicly available data on failures to deliver, we find that stocks reaching threshold levels of failures become significantly overvalued. Where short sale constraints are especially binding, we report extreme overpricing and subsequent reversals. These findings support the overvaluation hypothesis, although the mispricing is likely to be difficult to arbitrage because of extreme shorting costs. In addition, threshold stocks with low short interest become more overvalued than threshold stocks with high short interest. This suggests that the level of short interest reflects supply‐side effects when the examination conditions on the difficulty of borrowing shares.