Communications spectrum—that is, the set of electromagnetic frequencies suitable for communications and radar—is a precious resource. Like oil,it is limited and has a far-reaching impact on economic activity and national security. However, unlike oil, it cannot be stored for later use, and it cannot be exported, although it can be reused. Depending on the licensing regime, spectrum can have the characteristics of a private good or a common good. Spectrum can also be locally traded, and it can, by application of scientific creativity, be made more productive. Much research needs to be done in order to achieve the fullest possible productivity.