New Hart-Scott-Rodino premerger notification rules, which took effect in February, require that companies now provide more information than ever before about their prospective mergers. Meanwhile, both federal and state antitrust enforcers continue to step up scrutiny of data-related antitrust harms such as information sharing, monopolization, and price coordination, and private litigants are also filing claims. Data has long been used by companies to benchmark performance metrics, from pricing to inventory levels, and to manage revenue. But as data volume has increased, so too has the risk of violating antitrust laws through higher levels of interconnection. Big data could facilitate price coordination, potentially rising to the level of price fixing, and could thus entrench the market power of companies that have amassed data critical to the ability to compete.