High-definition digital radio is booming in the UK, offering crystal-clear sound and a wider range of listening options. But even though many American stations are now broadcasting in HD, consumers are largely unaware that the format even exists. “While the U.K. government — which controls much of the country’s broadcasting industry — was able to influence a national shift to digital, for-profit U.S. broadcasters were hesitant to embrace the unproven and expensive technology until satellite radio emerged as a competitive threat.”