A leading media buyer has downgraded its growth forecast for advertising spending in the U.S. to 3.5 percent. ZenithOptimedia [1], which is owned Publicis Groupe, had already rolled back its initial growth forecast for 2008 from 4.1 percent to 3.7 percent in March.

The latest downgrade is due to an uncertain U.S. economy and accelerated slowdown in consumer magazine advertising, according to the Zenith report.

“The credit crunch continues to worry investors, consumers and advertisers in Western markets,” the report states. “High energy and commodity prices are stoking inflation, so real growth—after adjusting for inflation—is unlikely to exceed 1%” in either the U.S. or Western Europe. 

But the company expects global internet ad spending to grow 26.7 percent this year, and will surpass its prediction that online ads will account for 12.3 percent of all advertising spending by 2010. Zenith now puts that number at 13.6 percent.