Thomas G. Wollmann

About

I am an Associate Professor of Economics and William Ladany Faculty Scholar at the University of Chicago Booth School of Business and a Faculty Research Fellow at the National Bureau of Economic Research ("NBER"). I graduated from Harvard with a PhD in 2015. My main field of study is industrial organization economics. 

PhD students on the 2025 job market

I am the Chair of Fern Ramoutar's Dissertation Committee. Fern is an exceptional PhD student. Fern intersects IO with urban and real estate economics. Her job market paper is extremely provocative---it establishes that landlords have acquired and exercised market power in US apartment rental markets. This is surprising because legislators have traditionally assumed away anticompetitive effects in real estate, going as far as to carve them out from the premerger notification program (see below for why that matters). Visit her website here. Update: Fern is joining University of Toronto as an Asst. Professor of Economics!

"Stealth consolidation" in plain language 

My ongoing work identifies a loophole in US antitrust law, which results in what I call "stealth consolidation." While a merger's size does not directly affect its legality, it does affect whether it's reported to the government. For instance, federal authorities are not notified of US mergers valued below $110MM. In highly segmented industries, however, even minor deals can produce major changes in market structure, firm behavior, and consumer welfare. (To fix ideas, think of a dialysis provider that has acquired all competing facilities in a commuting zone, which has happened many times.) Briefly, my work shows that mergers not subject to notification requirements almost completely escape antitrust scrutiny---the rate they are investigated by falls by around 90%. Compounding problems, when competitors know they are unlikely to face scrutiny, they are more likely to merge. In other words, when notification requirements are reduced, deterrence falls as well. My work also shows that, in aggregate, nonreportable mergers concentrate ownership and harm consumers. It further shows that notification requirements are especially low among acquisitions backed by private equity due to the idiosyncratic treatment of their investment structures. Since there is no "clearinghouse" for mergers, the full scale and scope of stealth consolidation is not yet known. 

Policy proposals and changes have followed.

2019: In Congress, Senator Blumenthal discussed legislation targeting nonreportable mergers (see the Subcommittee hearings at 1:36:00 that mention my earliest findings here). 

2020: FTC issued special orders citing concerns about "stealth consolidation" and compelling "big technology" firms to disclose previously nonreportable deals (see the Commissioners' joint statement here). 

2021: FTC restored its policy of prior approval that it had rescinded in 1995, citing similar concerns (see, e.g., the Federal Register for the Proposed Consent Agreement here). 

2023: FTC filed suit alleging an unlawful rollup of anesthesiology practices, with Chair Khan stating that the agency “will continue to scrutinize and challenge . . . stealth consolidation schemes that unlawfully undermine fair competition and harm the American public" (emphasis added; see a summary here). 

2023: FTC/DOJ "proposed the most significant changes to the [notification] rules since they were first implemented in 1978" (see, e.g., summaries by Kirkland & Ellis and Skadden here and here or the Federal Register NPRM at 42203 here). 

2023: US submits to OECD Directorate note that enumerates "remedies and solutions" for concerns identified by my research (see "stealth consolidation" in the first sentence and text surrounding footnotes 1 and 11 here).  

2024: Various states have passed bills creating their own, targeted notification programs. New York and Washington are examples (see, e.g., here). Illinois has enacted the most recent of which I am aware (see the legislative summary here).

Some media coverage of my work on this topic...

1. The Wall Street Journal (page 2 of the June 6, 2019 edition) provides a summary of my earliest findings [PDF].

2. Bloomberg  relates these findings to "big tech" acquisitions [link] and to Facebook in particular [link].

3. ADWEEK also provides a clear description of the implications for large technology companies [link].

4. The Financial Times  relates stealth consolidation to the death of the Dark Sky app [link]. 

5. USA Today describes it in the context of PE-backed healthcare acquisitions [link].

Curriculum vitae

Link to CV

Research

Trucks without Bailouts: Equilibrium Product Characteristics for Commercial Vehicles

American Economic Review, 2018, 108(6): 1364-1406

Stealth Consolidation: Evidence from an Amendment to the Hart-Scott-Rodino Act

American Economic Review: Insights, 2019, 1(1): 77-94.

The Impact of Money on Science: Evidence from Unexpected NCAA Football Outcomes

(with Haris Tabakovic) Journal of Public Economics, October 2019, Volume 178.  [PDF]

Does entry remedy collusion? Evidence from the generic prescription drug cartel 

(with Amanda Starc) American Economic Review, 2025, 115(5): 1400-1438. [PDF]

Terms of the Deal Were Not Announced: Accounting for Mergers with Unpublicized Values

AEA Papers and Proceedings, January 2023.

Entry Barriers, Personal Relationships, and Cartel Formation: Generic Drugs in the United States

(with Emily Cuddy, Rob Porter, & Amanda Starc)

in Cartels Diagnosed: New Insight on Collusion, Cambridge Univ. Press, 2023. 

A New Era of Midnight Mergers: Antitrust Risk and Investor Disclosures

(with John Barrios), American Economic Journal: Microeconomics, November 2024, 16(4).

Misaligned Measures of Control: Private Equity’s Antitrust Loophole

(with Aslihan Asil & John Barrios), Virginia Law & Business Review, Fall 2023, 18(1): 51-94.

Can Machines Commit Crimes Under US Antitrust Laws? 

(with Aslihan Asil) University of Chicago Business Law Review, 2023, 3(1): 1-38.

How to Get Away with Merger: Stealth Consolidation and Its Real Effects on US Dialysis

Journal of Political Economy (revise and resubmit), February 2024.

From Revolving Doors to Regulatory Capture? Evidence from Patent Examiners

(with Haris Tabakovic), American Economic Journal: Policy (revise and resubmit), July 2024.

Are Private Equity Funds Liable for Anticompetitive Acquisitions? 

(with Aslihan Asil, Paulo Ramos, & Amanda Starc), 

Stanford Journal of Law, Economics, and Business, forthcoming. 

How Merger Synergies Can Harm Consumers: A Defense of the Efficiency Offense 

(with Paulo Ramos), NBER Working Paper 32630, June 2024. 

Painful Bargaining: Evidence from Anesthesia Rollups

(Aslihan Asil, Paulo Ramos, & Amanda Starc) NBER Working paper 33217, April 2025.

Teaching

Competitive Strategy (42001)

The course applies microeconomics—mainly industrial organization economics—to analyze decisions managers face in business environments. The first half of the course takes a "price theory" approach to managerial decision-making. The actions of rivals are mostly assumed fixed, so we can isolate key tradeoffs that firms face. The second half employs game theory approach. Firms' actions directly affect their rivals payoffs, and vice versa, which allows us to address strategic interactions. Topics include pricing, positioning, entry and exit, vertical integration (i.e., the “make or buy” decision), commitment, cooperation, deterrence, network effects, multi-sided platforms, and antitrust considerations. 

The class is very interactive. Lectures comprise only about one-third of each week's class. The majority of time is devoted to case discussion, which include Moneyball; Cola Wars Continue; Airborne Express; Enterprise Rent-a-Car; Birds Eye and the UK Frozen Foods Industry; Baker and Hubbard: Monitoring Truckers; US Airline Industry in 1995; American Airlines; Intel Kickbacks; Dogfight over Europe: Ryanair; Power Play: Nintendo in 8-Bit Video Games; LinkedIn in 2012; Dropbox: It Just Works; Ridesharing. 

[Access syllabus here. Access week 1's readings and reading guide here.]