Confronting Consummated Mergers: An Inquiry into Policy and Practice

• Pages: 593-627
• Date: 01 January 2026
• Published date: 01 January 2026
• Author: John Kwoka,Tommaso Valletti
• Subject Matter: Administrative & Public Law

CONFRONTING CONSUMMATED MERGERS:

AN INQUIRY INTO POLICY AND PRACTICE

J K

T V*

INTRODUCTION ......................................... 594

I. POLICY TOWARD CONSUMMATED MERGERS .......... 597

A. E P E S .................... 597

B. C P  C M ....... 602

C. E A V E P M C:

K C ............................... 604

II. OPTIMAL TIMING OF MERGER CONTROL .............. 607

A. B C: E A P O .................... 608

B. C 2: E P R ............................ 608

C. C 3: H S ............................. 609

D. C 4: T I D  M ............... 610

III. POSTMERGER ACTIONS: THE U.S. EXPERIENCE ........ 610

A. F A E A V E P A ... 611

B. T CMAE D .................................. 612

C. R  R ............................. 618

CONCLUSIONS .......................................... 623

APPENDIX .............................................. 625

* Northeastern University and Imperial College London, respectively. The authors would

like to thank the editors and three anonymous reviewers, as well as Jack Collison, Maarten Pieter

Shinkel, Jennifer Sturiale, Spencer Weber Waller, and participants in the 2024 Loyola Antitrust

Colloquium, the 2024 EARIE Conference, and the 2025 International Industrial Organization

Conference for helpful comments on earlier drafts. We also want to express our appreciation

to Mirko De Maria, Diana Li, and Dayanara Diaz Vargas for invaluable research assistance.

Tommaso Valletti acknowledges the support of the Leverhulme Trust. The authors declare no

conflicts of interest.

593

INTRODUCTION

U.S. antitrust policy has undergone major changes in the past several years.

In 2023, the Federal Trade Commission (FTC) and the Antitrust Division of

the Department of Justice (DOJ) issued revised merger guidelines that include

a broader set of competitive concerns for triggering investigations and pos-

sible challenges.1 Both agencies have launched novel investigations and

pursued new legal and economic theories for challenging competitively prob-

lematic mergers and company behavior.2 Both declared their determination to

eschew merger remedies of dubious effectiveness.3 But not surprisingly, not

all important issues have been addressed. One significant gap concerns policy

toward consummated mergers that pose competitive problems.

To be sure, the overwhelming majority of consummated mergers pose no

competitive concerns. Yet some do, and the permissiveness of merger-control

policy has likely enlarged the problem. But apart from that, there are several

reasons that anticompetitive consummated mergers arise more generally. For

one, countless mergers fall below the legal threshold requiring prenotification

to the agencies,4 and recent research suggests that an unusually large fraction

of those lie just below the threshold and are competitively problematic but get

no antitrust scrutiny.5 Beyond that, the agencies conduct substantial investi-

gations of about 50 mergers per year.6 This number scarcely varies with the

1 See U.S. D’  J. & F. T C’, M G (2023), www.

justice.gov/atr/2023-merger-guidelines.

2 See, for example, the FTC’s challenge to the proposed merger of two supermarket chains

on the basis of labor market concerns and its complaint against Southern Glazer’s for violations

of the Robinson Patman Act. See FTC v. Kroger Co., No.3:24-CV-00347, 2024 WL 5053016, at

*31–32 (D. Or. Dec. 10, 2024) (discussing the labor market allegation and enjoining the merger

on other grounds); Complaint, FTC v. S. Glazer’s Wine & Spirits, LLC, No. 8:24-cv-02684

(C.D. Cal. Dec. 12, 2024), Dkt. No.1.

3 See, e.g., Jonathan Kanter, Assistant Att’y Gen., Antitrust Div., U.S. Dep’t of Just., Remarks

to the New York State Bar Association Antitrust Section (Jan. 24, 2022), www.justice.gov/opa/

speech/assistant-attorney-general-jonathan-kanter-antitrust-division-delivers-remarks-new-

york; Margaret Harding McGill, FTC’s New Stance: Litigate, Don’t Negotiate, A (June8,

2022), www.axios.com/2022/06/09/ftcs-new-stance-litigate-dont-negotiate-lina-khan (quoting

then-FTC Chair Lina Kahn).

4 To give an order of magnitude, in 2023 there were around 15,000 M&A transactions in

the United States. See United States - M&A Statistics, I. F M, A &

A., imaa-institute.org/mergers-and-acquisitions-statistics/united-states-ma-statistics (last

visited Feb. 3, 2026). Of these, only 1,805 were reported to the agencies—just 12% of the total.

See F. T C’ & D’  J., H-S-R A R: F

Y 2023, at1 (2024), www.ftc.gov/system/files/ftc_gov/pdf/fy2023hsrreport.pdf.

5 See generally Thomas G. Wollman, Stealth Consolidation: Evidence from an Amendment

to the Hart-Scott-Rodino Act, 1 A. E. R. 77 (2019); Thomas G. Wollman, How to Get

Away with Merger: Stealth Consolidation and Its Effects on US Healthcare (Nat’l Bureau of

Econ. Rsch., Working Paper No.27274, 2024), www.nber.org/papers/w27274 (analyzing the

effects of stealth consolidation on the U.S. healthcare industry).

6 See F. T C’ & D’  J., H-S-R A R:

F Y 2024, app. A (2025), www.ftc.gov/system/files/ftc_gov/pdf/FY24-HSR-ANNUAL-

REPORT-FOR-TRANSMITTAL-TO-CONGRESS.pdf.

594 A L J [Vol. 87

overall volume of reported mergers, suggesting that in years with an unusu-

ally large number of mergers, some escape scrutiny simply because of agency

resource constraints.7

Other reasons why anticompetitive consummated mergers arise include

the probability of agency error for those mergers subject to close examina-

tion. Indeed, recent meta-analyses of all published merger retrospectives

reported that 50% of all investigated—and cleared—mergers resulted in price

increases, suggesting underenforcement.8 These errors of omission result in

an ever-growing number of anticompetitive mergers. And finally, most merg-

ers that are predicted to be anticompetitive are not in fact prohibited. Rather,

most are allowed to proceed subject only to a structural or conduct remedy

that supposedly resolves the competitive issues. Evidence and experience

now demonstrate that both types of remedy, but especially conduct remedies,

suffer from significant failure rates.9

The result of these errors, imperfections, and slippages is that each year

the vast number of consummated mergers—large and small, reported and

not reported, investigated or not—includes some that ultimately raise com-

petitive concerns. Merger control at most antitrust agencies is, of course,

7 See generally J K, C M  M P 42–46 (2020);

Logan Billman & Steven C. Salop, Merger Enforcement Statistics: 2001–2020, 85 A

L.J. 1, 17 (2023); Filippo Lancieri & Tommaso Valletti, Towards an Effective Merger Review

Policy: A Defence of Rebuttable Structural Presumptions, 40 O R. E. P’ 763,

763–64 (2024). These sources report similar figures: Out of the 345,000 M&A transactions that

took place in the United States over the past 20 years, 9% were notified to the agencies, 0.3%

cases were scrutinized in detail, and 0.1% of them were blocked. European data are alike. See

Gabor Koltay, Szabolcs Lorincz & Tommaso Valletti, Concentration and Competition: Evidence

from Europe and Implications for Policy, 19 J. C L. & E. 466, 487–492 (2023).

8 For general surveys, see Malcolm B. Coate, A Retrospective on Merger Retrospectives in

the United States, 12 J. C L. & E. 209, 214–15 (2016); K, supra note 7,

at42–46; Annika Stöhr, Price Effects of Horizontal Mergers: A Retrospective on Retrospectives,

20 J. C L. & E. 155, 162–163 (2024). For specific ex post merger assess-

ments, among others, see Elena Argentesi et al., Merger Policy in Digital Markets: An Ex Post

Assessment, 17 J. C L. & E. 95 (2021); Orley Ashenfelter & Daniel Hosken, The

Effect of Mergers on Consumer Prices: Evidence from Five Mergers on the Enforcement Margin,

53 J.L. & E. 417 (2010); Orley C. Ashenfelter, Daniel S. Hosken & Matthew C. Weinberg,

Efficiencies Brewed: Pricing and Consolidation in the US Beer Industry, 46 RAND J. E. 328

(2015); Jonas Björnerstedt & Frank Verboven, Does Merger Simulation Work? Evidence from

the Swedish Analgesics Market, 8 A. E. J. 125 (2016); Nathan H. Miller & Matthew C.

Weinberg, Understanding the Price Effects of the MillerCoors Joint Venture, 85 E

1763 (2017).

9 See generally Argentesi et al., supra note 8; Markus Dertwinkel-Kalt & Christian Wey,

Evidence Production in Merger Control: The Role of Remedies, 59 R. I. O. 1, (2021);

Tomaso Duso, Klaus Gugler & Burcin Yurtoglu, EU Merger Remedies: An Empirical Assessment,

in 282 C  E A: T P E  A

303 (Vivek Ghosal & Johann Stennek eds., 2007); Richard Friberg & André Romahn, Divesti-

ture Requirements as a Tool for Competition Policy: A Case from the Swedish Beer Market, 42

I’. J. I. O. 1 (2015); J K, M, M C,  R:

A R A  U.S. P (2015); F. David Osinski & Jeremy A. Sandford,

Evaluating Mergers and Divestitures: A Casino Case Study, 37 J.L. E. & O. 239 (2021).

2026] C C M 595