ZenithOptimedia has significantly lowered its projections for ad spending in 2006, predicting that U.S. spending will grow only 2.9 percent, compared with a 3.6 percent gain it predicted when it released its previous update on Oct. 24, reports MediaPost (via MediaBuyerPlanner). Worldwide ad spending is now expected to grow only 4.8 percent, compared with ZenithOptimedia's previous forecast of 5.2 percent growth.

However, it increased its prediction regarding the advertising share that will be taken by online ad spending in 2005: up to 4.6 percent from the previously forecast 4.3 percent.

It also now predicts that by 2008 the internet will account for 6.4 percent of global ad spending. "From 2005 to 2008 inclusive, we predict it will create $15.8 billion new ad dollars - 17 percent of total global ad growth over this four-year period," said the agency.

Late last week, Merrill Lynch also revised ad growth predictions downward, predicting a 2006 growth of 4.5 percent, down from 5.2 percent.