Magna’s Bob Coen has revised his forecast for online ad spending downward—he now sees 12 percent growth for online advertising this year, where back in December, he predicted a 16.5 percent rise over 2007. In terms of dollar amounts, Coen, formerly director of forecasting at IPG sibling agency Universal-McCann, expects online ad dollars to come in at $11.7 billion. The reasoning behind the downgrade is not surprising, as Coen cites the pain marketers are feeling from the struggling economy.

SEE ALSO: Online Ads’ Global Share To Break 10 Percent Mark In ‘08; Internet Ads To Rise 26.7 Percent: Zenith

Overall, Coen also pulled back expectations for total U.S. ad increases in 2008: he now says national ad spend will gain 2 percent ($285 billion) instead of his December forecast calling for a 3.7 percent rise ($294 billion). Worldwide ad spend has been revised slightly: now it’s going to be up 4.4 percent ($667.9 billion), Coen says; previously, he believed global ad revenues would grow 4.6 percent ($653.9 billion).

As with most forecasts, it’s hard to make comparisons. Coen’s internet numbers are strictly U.S., so while it looks like Publicis Groupe’s ZenithOptimedia forecast last month appears significantly more rosy, it’s primarily due to a global view that sees more growth emerging markets. Zenith is forecasting internet ad spend to grow 26.7 percent and break through the 10 percent share barrier this year. And back in May, though, Lehman Brothers analyst Doug Anmuth also lowered his expectations for internet ad spend, saying online growth in the U.S. will be up 23 percent, down from his previous call for a 24 percent increase.