The Journal of Finance

A Theory of Trading Volume

Published: 12/01/1986   |   DOI: 10.1111/j.1540-6261.1986.tb02531.x

JONATHAN M. KARPOFF

A theory of trading volume is developed based on assumptions that market agents frequently revise their demand prices and randomly encounter potential trading partners. The model describes two distinct ways informational events affect trading volume. One is consistent with conjectures made by empirical researchers that investor disagreement leads to increased trading. But the observation of abnormal trading volume does not necessarily imply disagreement, and volume can increase even if investors interpret the information identically, if they also have had divergent prior expectations. Simulation tests support the model and are used to contrast the random‐pairing environment with costless market clearing. Volume is lower in the costly market, and volume increases caused by an informational event persist after the event period. This is consistent with existing empirical evidence and suggests that markets do not immediately clear all orders or that investors have demands to recontract.

Institutional and Legal Context in Natural Experiments: The Case of State Antitakeover Laws

Published: 12/15/2017   |   DOI: 10.1111/jofi.12600

JONATHAN M. KARPOFF, MICHAEL D. WITTRY

We argue and demonstrate empirically that a firm's institutional and legal context has first‐order effects in tests that use state antitakeover laws for identification. A priori, the size and direction of a law's effect on a firm's takeover protection depends on (i) other state antitakeover laws, (ii) preexisting firm‐level takeover defenses, and (iii) the legal regime as reflected by important court decisions. In addition, (iv) state antitakeover laws are not exogenous for many easily identifiable firms. We show that the inferences from nine prior studies related to nine different outcome variables change substantially when we include controls for these considerations.

Short Sellers and Financial Misconduct

Published: 09/21/2010   |   DOI: 10.1111/j.1540-6261.2010.01597.x

JONATHAN M. KARPOFF, XIAOXIA LOU

We examine whether short sellers detect firms that misrepresent their financial statements, and whether their trading conveys external costs or benefits to other investors. Abnormal short interest increases steadily in the 19 months before the misrepresentation is publicly revealed, particularly when the misconduct is severe. Short selling is associated with a faster time‐to‐discovery, and it dampens the share price inflation that occurs when firms misstate their earnings. These results indicate that short sellers anticipate the eventual discovery and severity of financial misconduct. They also convey external benefits, helping to uncover misconduct and keeping prices closer to fundamental values.

Takeover Defenses of IPO Firms

Published: 12/17/2002   |   DOI: 10.1111/0022-1082.00482

Laura Casares Field, Jonathan M. Karpoff

Many firms deploy takeover defenses when they go public. IPO managers tend to deploy defenses when their compensation is high, shareholdings are small, and oversight from nonmanagerial shareholders is weak. The presence of a defense is negatively related to subsequent acquisition likelihood, yet has no impact on takeover premiums for firms that are acquired. These results do not support arguments that takeover defenses facilitate the eventual sale of IPO firms at high takeover premiums. Rather, they suggest that managers shift the cost of takeover protection onto nonmanagerial shareholders. Thus, agency problems are important even for firms at the IPO stage.

Short Selling and Earnings Management: A Controlled Experiment

Published: 10/13/2015   |   DOI: 10.1111/jofi.12369

VIVIAN W. FANG, ALLEN H. HUANG, JONATHAN M. KARPOFF

During 2005 to 2007, the SEC ordered a pilot program in which one‐third of the Russell 3000 index were arbitrarily chosen as pilot stocks and exempted from short‐sale price tests. Pilot firms’ discretionary accruals and likelihood of marginally beating earnings targets decrease during this period, and revert to pre‐experiment levels when the program ends. After the program starts, pilot firms are more likely to be caught for fraud initiated before the program, and their stock returns better incorporate earnings information. These results indicate that short selling, or its prospect, curbs earnings management, helps detect fraud, and improves price efficiency.