NEW YORK (AdAge.com) -- One media agency has trimmed its 2007 ad-spending forecast for North America and Western Europe, partly as a result of advertisers' ongoing shifts toward -- wait for it -- new media.

"The shift in publishers' investment from print to the internet now leads us to expect no growth from newspapers in the U.S. this year, and less growth from magazines than we forecast in December," said the agency, ZenithOptimedia, in its updated April forecast. Zenith now expects that North America will see ad spending of $189.6 billion this year, up 3.5% from 2006. In December, the Publicis Groupe agency had predicted $190.8 billion in North America ad spending, an increase of 4.2% over 2006.

Global ad spending, meanwhile, will grow 5.2% to reach $454.9 billion, Zenith estimated, including $167.8 billion for TV, $126.2 billion for newspapers, $56.4 billion for magazines, $36.3 billion for radio and $31.3 billion for the web.

"We now expect the internet to overtake radio in 2008, a year earlier than in our last forecast," Zenith said. "We forecast the internet to account for nearly 9% of global ad spend by 2009, and its share should reach double digits early next decade."

There was good news for TV, however, in the updated forecast. "Last December we voiced concerns that television was about to enter its first-ever sustained period of market-share loss at the global level," the agency said. "Demand has picked up since then, and we have revised our forecasts for television expenditure upwards." Zenith now expects that TV's share of global ad spending in 2009 will be only 0.2% lower than it was in 2005.

The quadrennial combination of the summer Olympics, U.S. presidential elections and the European football championship will lift 2008 ad-spending growth to 6.2% that year, according to Zenith, followed by a more typical 5% in 2009.