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We analyze the role of retail investors in stock pricing using a database uniquely suited for this purpose. The data allow us to address selection bias concerns and to separately examine aggressive (market) and passive (limit) orders. Both aggressive and passive net buying positively predict firms' monthly stock returns with no evidence of return reversal. Only aggressive orders correctly predict firm news, including earnings surprises, suggesting they convey novel cash flow information. Only passive net buying follows negative returns, consistent with traders providing liquidity and benefiting from the reversal of transitory price movements. These actions contribute to market efficiency.

Just as employers face uncertainty when hiring workers, workers also face uncertainty when accepting employment, and bad employers may opportunistically depart from expectations, norms, and laws. However, prior research in economics and information sciences has focused sharply on the employer’s problem of identifying good workers rather than vice versa. This issue is especially pronounced in markets for gig work, including online labor markets, in which platforms are developing strategies to help workers identify good employers. We build a theoretical model for the value of such reputation systems and test its predictions on Amazon Mechanical Turk, on which employers may decline to pay workers while keeping their work product and workers protect themselves using third-party reputation systems, such as Turkopticon. We find that (1) in an experiment on worker arrival, a good reputation allows employers to operate more quickly and on a larger scale without loss to quality; (2) in an experimental audit of employers, working for good-reputation employers pays 40% higher effective wages because of faster completion times and lower likelihoods of rejection; and (3) exploiting reputation system crashes, the reputation system is particularly important to small, good-reputation employers, which rely on the reputation system to compete for workers against more established employers. This is the first clean field evidence of the effects of employer reputation in any labor market and is suggestive of the special role that reputation-diffusing technologies can play in promoting gig work, in which conventional labor and contract laws are weak. This paper was accepted by Chris Forman, information science.

The efficient markets theory reached the height of its dominance in academic circles around the 1970s. Faith in this theory was eroded by a succession of discoveries of anomalies, many in the 1980s, and of evidence of excess volatility of returns. Finance literature in this decade and after suggests a more nuanced view of the value of the efficient markets theory, and, starting in the 1990s, a blossoming of research on behavioral finance. Some important developments since 1990 include feedback theories, models of the interaction of smart money with ordinary investors, and evidence on obstacles to smart money.

Revolutions often spawn counterrevolutions and the efficient market hypothesis in finance is no exception. The intellectual dominance of the efficient-market revolution has more been challenged by economists who stress psychological and behavorial elements of stock-price determination and by econometricians who argue that stock returns are, to a considerable extent, predictable. This survey examines the attacks on the efficient market hypothesis and the relationship between predictability and efficiency. I conclude that our stock markets are more efficient and less predictable than many recent academic papers would have us believe.

Limited attention theory predicts that higher salience of earnings news implies a stronger immediate market reaction to earnings news and a weaker post-earnings announcement drift (PEAD) or reversal (PEAR). Using a new measure, SALIENCE, defined as the number of quantitative items in an earnings press release headline, we find strong evidence consistent with salience effects. Higher SALIENCE is associated with stronger announcement reaction and subsequent PEAR. Managers are more likely to choose higher SALIENCE before selling shares in the post-announcement period and when earnings are high, but less persistent, and to choose lower SALIENCE before stock option grants. The results are robust to using residual salience and an extended set of control variables. The findings are consistent with managers opportunistically headlining positive financial information in the earnings press release to incite over-optimism in investors with limited attention.

A question of increasing interest to researchers in a variety of fields is whether the biases found in judgment and decision-making research remain present in contexts in which experienced participants face strong economic incentives. To investigate this question, we analyze the decision making of National Football League teams during their annual player draft. This is a domain in which monetary stakes are exceedingly high and the opportunities for learning are rich. It is also a domain in which multiple psychological factors suggest that teams may overvalue the chance to pick early in the draft. Using archival data on draft-day trades, player performance, and compensation, we compare the market value of draft picks with the surplus value to teams provided by the drafted players. We find that top draft picks are significantly overvalued in a manner that is inconsistent with rational expectations and efficient markets, and consistent with psychological research. This paper was accepted by Uri Gneezy, behavioral economics.

In Chinese culture, certain digits are lucky and others unlucky. We test how such numerological superstition affects financial decision in the China initial public offering (IPO) market. We find that the frequency of lucky numerical stock listing codes exceeds what would be expected by chance. Also consistent with superstition effects, newly listed firms with lucky listing codes experience inferior post-IPO abnormal returns. Further tests suggest that our conclusions are not driven by endogeneity. This paper was accepted by Lauren Cohen, finance .

Recent models and the popular press suggest that large groups of hedge funds follow similar strategies resulting in crowded equity positions that destabilize markets. Inconsistent with this assertion, we find that hedge fund equity portfolios are remarkably independent. Moreover, when hedge funds do buy and sell the same stocks, their demand shocks are, on average, positively related to subsequent raw and risk-adjusted returns. Even in periods of extreme market stress, we find no evidence that hedge fund demand shocks are inversely related to subsequent returns. Our results have important implications for the ongoing debate regarding hedge fund regulation. This paper was accepted by Wei Jiang, finance.

How does competition in firms' product markets influence their behavior in equity markets? Do product market imperfections spread to equity markets? We examine these questions in a noisy rational expectations model in which firms operate under monopolistic competition while their shares trade in perfectly competitive markets. Firms use their monopoly power to pass on shocks to customers, thereby insulating their profits. This encourages stock trading, expedites the capitalization of private information into stock prices and improves the allocation of capital. Several implications are derived and tested.

Stock-market trading is increasingly dominated by sophisticated professionals, as opposed to individual investors. Will this trend ultimately lead to greater market efficiency? I consider two complicating factors. The first is crowding—the fact that, for a wide range of \"unanchored\" strategies, an arbitrageur cannot know how many of his peers are simultaneously entering the same trade. The second is leverage—when an arbitrageur chooses a privately optimal leverage ratio, he may create a fire-sale externality that raises the likelihood of a severe crash. In some cases, capital regulation may be helpful in dealing with the latter problem.