A New Era of Midnight Mergers

Abstract

Antitrust authorities discover anticompetitive mergers largely by searching public documents, so the same disclosures investors rely on can alert regulators to deals that would otherwise go unnoticed. That gives managers a reason to keep some transactions quiet. We study this behavior in publicly traded U.S. firms.

Using a regression-discontinuity design around the threshold—10% of the acquirer's assets—that makes detailed Item 2 disclosure mandatory, we show that reporting a deal to investors carries real antitrust risk: mandatory disclosure raises the chance a merger is detected and sharply lowers the share of horizontal mergers just above the threshold. We then measure undisclosed mergers from firms' financial-accounting reporting requirements and find they total $1.85 trillion between 2002 and 2016, about 38% of merger value—so standard counts understate consolidation.

Key Findings

Disclosure Poses Antitrust Risk

Regulators find anticompetitive deals by reading public filings, so disclosing a merger raises its odds of scrutiny. Managers respond by staying quiet about some transactions.

A Sharp Discontinuity

At the 10%-of-assets threshold where Item 2 disclosure becomes mandatory, disclosure jumps about 37 percentage points and the share of horizontal mergers falls about 12 points, from 42% to 30%.

$1.85 Trillion in Undisclosed Mergers

Detecting deals through financial-accounting reporting requirements, we find undisclosed mergers total $1.85 trillion from 2002 to 2016—roughly 38% of merger value. Common measures miss them.

Rules at Cross-Purposes

Investor disclosure and antitrust detection draw on the same information, so the SEC's transparency goals and FTC/DOJ enforcement can work against each other.

Figures

Figure 1: Regression-Discontinuity Results

A fuzzy regression-discontinuity design around the threshold—10% of the acquirer's assets—that triggers a mandatory Item 2 filing. Panel A (first stage) shows that the share of mergers with an Item 2 report rises to 35% just below the cutoff and jumps discontinuously to 73% just above it, roughly a 37-percentage-point jump. Panel B (reduced form) shows the horizontal share of mergers falling about 12 percentage points at the cutoff, from 42% just below to 30% just above.

Figure 2: Strategic disclosure mechanism showing how firms choose among four disclosure levels—premerger (HSR) notification, Item 2 reports, basic disclosures, and undisclosed—in response to antitrust risk.

Data & Design

We study publicly traded U.S. firms. A merger whose transaction value reaches 10% of the acquirer's assets triggers a mandatory Item 2 filing, and we use a regression-discontinuity design around that cutoff to estimate the effect of disclosure. Separately, we build a measure of undisclosed mergers from firms' financial-accounting reporting requirements, which lets us count deals that never appear in standard merger data.

Citation

Barrios, John Manuel, and Thomas G. Wollmann. “A New Era of Midnight Mergers: Antitrust Risk and Investor Disclosures.” American Economic Journal: Microeconomics 16, no. 4 (2024).