IBiquity Digital recently said some 3 million HD Radio receivers have sold so far. Now ABI Research, which analyzes emerging technologies, predicts about 4 million HD Radio receivers will have shipped in the United States by the end of this year.

In Europe, led by Britain, governments have chosen the DAB standard and consumers have purchased nearly 13.5 million radio receivers, the firm said. By 2015, the worldwide installed base of digital radio receivers of all formats, excluding handsets, is expected to reach nearly 200 million units, ABI predicts.

“Smartphones are expected to include digital radio receivers starting in mid-2011, driven by carriers’ desire to offer users premium audio content while limiting the use of scarce radio spectrum,” stated senior analyst Sam Rosen. “This concern is demonstrated by AT&T’s decision to stop offering unlimited data plans, due largely to high data usage in New York and San Francisco resulting from Internet radio sites such as Pandora.”

ABI predicts digital radio technologies, including satellite radio and Internet radio, will reverse trends of decreasing listenership. Listeners will have access to niche programming targeted to narrower demographic segments and will respond to a more interactive user experience enabled by program guides and other enhancements. Broadcasters, in turn, will have a larger reach and the ability to provide better targeted and more interactive ads, ABI observes.

“The U.S. adoption of HD Radio began in the automotive sector, and then home, but finally extended into portables in 2010,” Rosen said. “The adoption of DAB radios in Europe has been led primarily by tabletop radio sales in the U.K.”

Switzerland, Denmark, and Norway have significant broadcast infrastructure in place, with Australia, Germany and France to complete the majority of their infrastructure in 2011, he said.