As users spend less time listening to the radio and more time online, advertisers are following them, cutting back on radio advertising and increasing their online spend, according to eMarketer.The eMarketer study found that advertisers will soon spend as much money on the internet as they do on the airwaves, Business Week reports. The research firm estimates that 2006 online advertising spending will reach $16.4 billion, or about 5.8 percent of the $281 billion advertisers are expected to spend this year, less than radio's 6.9 percent, according to Interpublic Group's Universal McCann. But the shift from radio to online is underway, with online ad spend expected to surpass that of radio by 2008.

In the first quarter of 2006, Americans reported spending more than an hour on the internet per day and less than half that time, 23 minutes, reading books and magazines, according to a September 2006 report by eMarketer's James Belcher.

Meanwhile, advertisers spent a combined 38.2 percent of their advertising budgets on magazines and newspapers in the first half of 2006. They spent only 6.4 percent on the internet during that same period. The trend toward users' spending more time online is expected to continue, with advertising budgets shifting as well.