Economic deregulation does not happen overnight. It takes time for lawmakers and regulators to dismantle regulatory regimes, and then it takes more time for the deregulated industries to adjust to their new competitive environment. Federal regulatory agencies and the U.S. Congress began liberalizing pricing, entry, and exit in the transportation, financial, energy, and communications industries during the mid-1970s. But while some smaller industries such as intercity bus transportation and air cargo have been fully deregulated during that time, the only major American industries fully deregulated to date are airlines and motor carriers. As to the pace of industry adjustment, consider airlines. Economic deregulation of the airline industry began in 1974 when the Civil Aeronautics Board first encouraged experiments with discount fares. It was completed in 1983 when all regulations on fares, entry, and exit were eliminated. Yet more than 20 years after the deregulatory process began, the airline industry continues to shed inefficiencies that accumulated over decades of regulation and to find new ways to market their service. Indeed, the airlines' latest marketing innovation-selling discount fares on the Internet-would be illegal if fares were still regulated.It is not surprising that deregulated (or partially deregulated) industries are slow to achieve maximum efficiency. When regulatory restrictions on pricing, operations, and entry (especially from new firms), have been enforced for decades, managers and employees of regulated firms settle into patterns of inefficient production and missed opportunities for technological advance and entry into new markets. Deregulation frees an industry from the state's control over prices, entry, and exit, although, of course, firms are still subject to antitrust laws and safety regulations. After deregulation, some costs usually fall in short order, but it takes Clifford Winston is Senior Fellow, Brookings Institution, Washington, D.C.