Chantilly, Va.—In 2012, over-the-air ad revenue for the radio industry inched up 1.5%, to $14.3 billion. However, online ad revenue, a much smaller share of overall revenue, soared almost 25%, to $491 million, marking online ad revenue at 3.3% of total revenue last year, according to a market report published by BIA/Kelsey, which advises companies in the local media industry. For 2013, BIA/Kelsey forecast 2.3% over-the-air radio ad revenue growth, to $14.7 billion, due to the slightly stronger economy, along with approximately 20% growth in digital ad revenue, to about $600 million. The company's projections show radio stations' revenue mix continuing to shift to digital in the coming years. Income from online advertising is expected to rise at a rate of about 10.8% annually over the next five years versus 2.5% from over-the-air.