Economies in which dynamism comes from new firms historically have commercialized the radical innovations that keep pushing out the production-possibility frontier. Examples from the last two centuries include such transformative products and innovations as railroads, automobiles, and airplanes; telegraph, telephones, radio, and television; air conditioning; and, as just noted, the various technologies responsible for the IT revolution, including both mainframe and personal computers, routers and other hardware devices, and much of the software that operates them.