The term “Big Tech” is often used to describe the five largest multinational online service or computer hardware and software companies: Amazon, Apple, Facebook, Google, and Microsoft. These companies hold five of the top six slots, by market value, for publicly traded firms. The growth of Big Tech over the past three decades is a function of numerous forces. These range from economic phenomena such as network effects and winner-take-all markets, organic growth resulting from innovative business models and technologies, to expansion through a series of acquisitions of smaller, potential, or nascent rivals. While Big Tech has undoubtedly produced benefits, significant concerns have coalesced around it. The growth of Big Tech has created controversy over the companies’ role in our society and raised a suite of competition issues that are attracting attention from Congress and enforcers. These include effects on innovation and market entry; incentives to compete on price and non-price dimensions of competition such as privacy; and the potential for artificial intelligence-driven algorithmic pricing to facilitate coordinated conduct. The debate over the size and alleged dominance of Big Tech companies has promoted wideranging proposals to use the antitrust laws to break them up. But few of these proposals are driven by a methodological, fact-based analysis. Such analysis would explore the strategic competitive abilities and incentives that are specific to different Big Tech business models, how the companies compete in a variety of individual markets and clusters of related markets, and how alleged conduct potentially runs afoul of the U.S. antitrust laws. Breakup proposals therefore “put the cart before the horse” and fail to provide needed support for more vigorous antitrust enforcement and beneficial reform proposals. This American Antitrust Institute (AAI) White Paper offers a fact-based analysis of one important component of a broader assessment of the competitive issues surrounding Big Tech. It focuses on Big Tech’s acquisition of over 720 smaller, potential, and nascent rivals over almost the last three decades. As is typical of M&A activity, only a portion of these transactions were reportable to the U.S. antitrust agencies under the Hart Scott Rodino Act (HSR) federal premerger reporting requirements.8 A closer look at enforcement data for one major Big Tech industry category reveals that while the U.S. Department of Justice (DOJ) and Federal Trade Commission (FTC) appear to have subjected a higher than average number of transactions to more extensive agency investigation, only one deal has been challenged in federal court. It does not come as a surprise therefore that the record of U.S. merger enforcement in an important Big Tech industry category is far lower than the record across all sectors, as defined by the rate of merger challenges in federal court. This statistic warrants further inquiry. This White Paper does not investigate whether serial acquisitions by Big Tech companies have created dominance in certain markets, or if they engage in conduct that violates the antitrust laws. Those questions should be the subject of appropriately framed merger retrospectives and antitrust agency inquiries, including the DOJ’s reported investigation into Google. Rather, the analysis herein explores the various reasons why enforcement might be weaker in Big Tech and the policy implications raised by those explanations. The AAI has provided independent, in-depth legal, economic, and policy analysis of antitrust and competition issues for over 20 years. The organization has been outspoken on the issue of competition in the tech sector through its research, education, and advocacy agenda and initiatives. This White Paper begins with an empirical review of the acquisition history of Big Tech and the U.S. antitrust agencies’ limited record of merger enforcement in a major industry area in which many Big Tech firms operate. It then unpacks the limited merger enforcement record and examines why it can and should be invigorated.