• by Erik Sass  @eriksass1, May 19, 2013

Radio advertising revenues were flat at $3.5 billion in the first quarter of 2013, unchanged from the same period in 2012, according to the Radio Advertising Bureau, which cited weak demand in the first two months of the year, followed by stronger results in March. 

Total spot advertising revenue -- long the mainstay of the radio business -- was down 2% to $3 billion, while digital revenues increased 9% to $179 million and off-air revenues grew 5% to $338 million.

As in several recent quarters, the RAB was unable to report network ad revenues because Miller Kaplan Arase, which compiles the information and relies on voluntary disclosures by radio broadcasters, was not able to obtain data covering at least 90% of the market.

The top growth categories for radio in the first quarter were department and discount stores, up 58%, communications and cellular providers, up 36%, and financial services, up 13%. Home furnishings were up 6%. Conversely, automotive spending fell 20%, insurance companies were down 9%, health care slid 5%, beverages edged down 4%, concerts, theaters and movies were also down 4%, and TV, network and cable providers fell 3%.

While digital revenues are growing at a healthy clip, they remain a fairly small part of radio’s overall business, representing just 5.1% of radio’s total revenues in the first quarter of 2013. That’s up slightly from 4.7% of total revenues in the first quarter of 2012, excluding the network category. (When network was included in 2012 results, , digital was 4.3% of the total.)