In new research, Ricardo Perez-Truglia and Jeffrey Yusof study what drives Americans’ support for antitrust enforcement. They find that information about traditional consumer welfare harms, such as higher prices or less choice, has the largest and most durable impact.
A small number of very large companies have come to play an outsized role in the United States economy. Research using U.S. census data, for example, found that sales became more concentrated among the largest firms in every major sector between 1982 and 2012. By June 2026, the ten largest companies in the S&P 500 accounted for 43.2 percent of the index’s total market value, up from 17.8 percent in 2015.
Dominant firms can generate substantial benefits for consumers through scale, convenience, and innovation. But their market power can also produce the classic harms that motivate antitrust enforcement: higher prices, lower quality, less innovation, exclusion of rivals, and fewer choices. There has been a notable uptick in antitrust enforcement, involving some high-profile companies such as Google, Live Nation, and Meta.
Although antitrust is often treated as a technical field for lawyers and economists, public opinion matters. Lay juries sometimes decide private antitrust cases. More broadly, voters can influence elected officials who write antitrust laws, fund enforcement agencies, and oversee competition policy. Presidents appoint the leaders of the two U.S. antitrust agencies, the Federal Trade Commission and the Department of Justice, including officials who may favor more or less aggressive enforcement.
What, then, drives public demand for antitrust? In a new working paper, “Who Wants to Break Up Big Firms? Harm, Fairness, and the Demand for Antitrust,” we address these questions with a survey experiment. We recruited 4,016 Americans and randomly assigned each participant to one of five real antitrust cases: Google versus the DOJ, Meta versus the FTC, Live Nation versus the DOJ, Apple versus Epic Games, or a class action against eyewear company Luxottica.
After providing participants with a brief introduction to the case, we took an initial measure of four beliefs that might drive support for antitrust enforcement: the company’s perceived market share, the perceived harm to consumers, perceptions about unfair competitive practices, and the company’s overall image. Participants were then randomly assigned either to receive no additional information (the control group) or to receive fact-based information related to one of the four beliefs (the treatment groups).
For example, participants in the market-share treatment were told the company’s market share, which ranged from 60-84%, depending on the case. The consumer-harm treatment consisted of information arguing that the company’s market dominance harmed consumers through higher prices, reduced quality, or less innovation. The unfair-competition treatment argued that the company used unfair practices to gain its market dominance, such as through exclusive contracts or acquisitions of potential competitors. The negative-image treatment included information about a controversy that could affect the company’s overall image but was unrelated to competition, such as allegations of sexual misconduct by company executives.
After the treatment assignment, we re-elicited the four beliefs. Most importantly, we measured the subject’s attitudes towards antitrust: whether they sided with the plaintiff, and whether they supported remedies such as breaking up the company. We also asked about dominant firms and antitrust policy more generally. Some measures involved concrete actions, such as signing a petition, sending an email to a senator, or making a donation to an antitrust organization. And we conducted a follow-up survey a month later to measure the persistence of the treatment effects.
All four information treatments had significant effects on the beliefs they were designed to influence. For example, the market-share treatment increased the market share participants perceived the company to have by 6.8 percentage points, while the consumer-harm treatment increased perceived consumer harm, and so on. These results confirm that participants found the information credible and updated their views accordingly. However, the treatments had markedly different effects on demand for antitrust enforcement.
The consumer-harm treatment had the strongest overall effects. It increased support for the plaintiff by 0.45 standard deviations and support for remedies by 0.28 standard deviations. Its effects also extended beyond the assigned case: participants became more likely to believe that dominant firms generally harm consumers and more supportive of stronger antitrust enforcement. One month later, it was the only treatment with clear, statistically significant effects on both plaintiff support and remedy support.
The unfair-competition treatment increased plaintiff support by 0.48 standard deviations and remedy support by 0.33 standard deviations. However, these effects were narrower and less durable than those of the consumer-harm treatment. The negative-image treatment made participants more likely to side against the company and somewhat more supportive of remedies. But it generated little support for broader antitrust policy, and its main effects had largely disappeared one month later. Lastly, the market-share treatment had little to no effect.
Because a single treatment can shift multiple beliefs at once, we used an econometric approach called instrumental-variables to disentangle the causal effects of each of the four beliefs. The results reveal a clear hierarchy. Perceived consumer harm was the only belief that consistently increased support for the plaintiff, remedies, stronger enforcement in general, and broader competition policies. Perceived unfair competition increased demand for action in the assigned case but did not generalize as strongly. A negative image mainly shifted participants’ favorability toward the plaintiff, while perceived market share had no meaningful independent effect.
Overall, our findings suggest the public’s support for antitrust enforcement is broadly consistent with the standard economic framework. Consumer harm plays the central role: respondents do not favor antitrust action merely because a firm is large, but rather when they believe its market dominance harms consumers. Perceptions of unfairness, which fall outside the standard economic framework, also shape support for enforcement, although their effects are more limited in scope.
These findings may have practical implications for policymakers and regulators. Public arguments for antitrust often emphasize the sheer size or market share of dominant firms. Our results suggest that these facts alone are unlikely to build support for enforcement. Messages focused on prices, quality, and innovation may have stronger and more durable effects. Arguments centered on unfair practices may also resonate with the public.
Authors’ Disclosures: The authors report no conflicts of interest. You can read our disclosure policy here.
Articles represent the opinions of their writers, not necessarily those of the University of Chicago, the Booth School of Business, or its faculty.
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