<p>In 1977, at the age of 21, I wrote this article concerning the deterrent effect of antitrust treble damages. The paper attracted serious attention at the time, benefiting from comments by economic luminaries John Shoven, Bruce Owen, and Oliver Williamson, and receiving a formal accolade from Stanford University. In the decades that followed, my thinking on antitrust enforcement was further shaped by antitrust scholar Kenneth Elzinga and, most decisively, by Judge Richard Posner, for whom I later served as a law clerk. However, for reasons long forgotten—but surely in part because the internet did not exist until 1983—I did not disseminate this paper more widely. Eventually, I lost my only copy of the paper, which I had typed on an IBM Selectric; and thus I did not read it again until 2025, when librarians at Stanford tracked it down for me in the university’s archives. The paper’s publication in <i>The Criterion Journal on Innovation</i> these 49 years later now reflects a simple but telling fact: the relevant antitrust law on treble damages has not materially changed since 1977, and neither has the economic logic governing the deterrent effect of treble damages. To paraphrase Led Zeppelin, the math remains the same.</p> <p><span>Lawyers and economists have long argued that antitrust treble damages overdeter anticompetitive conduct and inefficiently chill lawful behavior. I question that conclusion by distinguishing between the nominal cost and the effective cost of treble damages to an antitrust defendant. When the economic analysis of antitrust deterrence properly considers inflation, interest income earned during litigation delay, the tax deductibility of damage payments, and uncertainty of detection and recovery, the effective cost to the antitrust violator diverges substantially from the 300-percent statutory benchmark in section 4 of the Clayton Act. Treble damages function in practice as an implicit tax on income derived from illegal conduct, but at an effective tax rate that is frequently far lower—and, in some circumstances, even negative. Consequently, the conventional overdeterrence critique advanced by Posner, Elzinga, and others since the 1970s loses force, and the concern that private antitrust enforcement is economically inefficient remains overstated.</span></p> <p><span>I further demonstrate that uncertainty discounts the </span><i>ex ante</i><span>&nbsp;deterrent effect of treble damages and might make antitrust violations a rational investment for risk-averse firms. Finally, I propose modest reforms—adjusting damages for inflation, limiting deductibility, and requiring compensation for forgone interest—that would materially increase the efficiency and deterrent value of treble damages without abandoning private enforcement.</span></p>