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The increase in investor diversity over the last 35-40 years (ICI 2014) prompted us to revisit trading volume reactions to earnings announcements and how these reactions vary with firm size. This increase in investor diversity would likely lead to an increase in differences in the precision of pre-announcement information and potentially increase the importance of earnings announcements to resolve investor disagreement. We find that the nature of trading volume reactions to earnings announcements has fundamentally changed over the 35-year time period 1977-2011. There has been a dramatic increase in the magnitude and frequency of volume reactions to earnings announcements over this time period, and this effect is more pronounced in large firms where volume reactions were previously infrequent. The increase in large firms’ trading volume reactions is so pronounced that the relation between volume reactions and firm size has turned positive in recent years, thereby reversing Bamber’s (1986, 1987) previously documented negative relation. We provide intuition and empirical evidence that our results are attributable to the resolution of differential prior precision among an increasingly diverse set of investors following large firms.

This paper reviews, synthesizes, and critiques the capital market literature examining trading volume around earnings announcements and other financial reports. Our purposes are to assess what we have learned from examining trading volume around these announcements and to suggest directions for future research. We conclude that researchers have yet to realize the potential Beaver (1968) identified for trading volume to yield unique insights regarding the nature of earnings announcements and other financial reports, and the effects of these announcements on market participants. This state of the literature is attributable to a dearth of volume theory early on, and more recently to a disconnect between theoretical development and empirical research. Thus, we begin by briefly summarizing developments in trading volume theory since Beaver (1968). We also discuss unique measurement challenges in trading volume research, including identifying appropriate proxies for abnormal trading volume and for individual investors’ beliefs. In light of theory and empirical measurement issues, we interpret the current literature and identify directions for future research. We conclude that extant research just scratches the surface of what trading volume can reveal about the characteristics of financial disclosures and the effects of these disclosures on investors.

This study provides evidence regarding the effects of online trading on stock price and trading volume reactions to quarterly earnings announcements. We test for differences in stock price and volume reactions to quarterly earnings announcements between a period with a significant amount of online trading (1996-99) and a period without online trading (1992-95). We conjecture that online trading has increased the proportion of naive investors in the market. We predict that this will result in (1) a decrease in the average precision of investor information prior to earnings announcements leading to higher earnings response coefficients (ERCs), (2) an increase in differential interpretation of earnings leading to higher trading volume reactions that are unrelated to price change, and (3) a decrease in differential prior precision leading to a decrease in the association between trading volume and absolute price change. We find evidence consistent with all three predictions. Our findings are relevant for assessing the validity of concerns about online trading expressed by regulators and the validity of theoretical models of trade with asymmetrically informed investors.

This paper examines how market prices, volume, and traders' dividend expectations respond to public information releases in laboratory markets for a long-lived financial asset. The objective is to study deviations from the symmetric information risk-neutral rational expectations (RE) benchmark, which predicts no trade in such settings. The results of a series of double-auction and call markets are reported in which traders manage a portfolio of cash and asset shares over 15 rounds of trading. A public signal regarding the value of the liquidating dividend is released every third round, and traders' subjective expectations of the liquidating dividend are elicited each round as cash-motivated forecasts. We find that, despite the public dividend signal, traders' dividend forecasts are heterogeneous. Forecasts and prices both underreact to the public signals, with prices under-reacting more than forecasts. In general, price changes are not closely associated with public signals, and there is greater excess price volatility in double auctions than in call markets. Forty-three percent of trades are inconsistent with the trader's forecasts, and inconsistent trades occur more frequently in the double-auction markets. On average, approximately 10 percent of the outstanding shares are traded in each round, and trading volume is increasing in the mean absolute forecast revision and decreasing in the contemporaneous dispersion in forecasts. These results suggest that differential processing of the public signal and/or speculative trading for short-term gain may help to explain why symmetric information RE predictions are often not supported in empirical and experimental settings. They also suggest that market reactions to public information releases may be influenced by market microstructure.