eMarketer, projects a 10.5% increase in US online ad spending next year, followed by double-digit growth every year through 2014 when spending will reach $40.5 billion.

Increases in online spending will far outpace those for total media spending, which are 3% this year and will inch up by 1.2% next year. In 2014, eMarketer estimates total media ad spending will be $188.5 billion, up from $168.5 billion this year.

eMarketer forecasts continuing shift toward online advertising despite cautiousness among advertisers due to the economy. Large brand marketers and SMBs are major contributors to ongoing increases.

“It may seem ironic, but marketers’ economic concerns are leading them to spend more for online advertising,” said David Hallerman, principal analyst at eMarketer. “This trend reflects how most forms of internet advertising are now seen as more of a ‘sure thing’ than most traditional media.”