• by Erik Sass  @eriksass1, January 4, 2011

It wasn't just your imagination: Geico was the biggest radio advertiser in 2010, with the ubiquitous discount insurance provider running a formidable 2.3 million broadcast radio spots over the course of the year, according to Media Monitors.

Listeners would probably recognize the runners-up, too. Home Depot came in second with 1.96 million broadcast radio spots, followed by McDonald's with 1.27 million. Verizon was in fourth place with 1.19 million spots.

Remarkably, the radio business itself took fifth place, with the HD Digital Radio Alliance airing 1.14 million spots -- most of which were contributed by participating broadcast radio groups, including big players like Clear Channel Radio, CBS Radio and Cox.

While public awareness of the new medium has increased, HD digital radio has struggled to break through in terms of consumer adoption over the last couple years.

The rest of the top 10 biggest radio advertisers included AutoZone, Walmart, AT&T, Kohl's and Subway.

While fourth-quarter results are not yet available, the broadcast radio business appears to have stabilized in 2010, following several years of steep declines. Through the end of the third quarter, year-to-date revenues increased 6% compared to the same period in 2009, from $12 billion to $12.7 billion, according to the Radio Advertising Bureau.