The survey has predicted that global advertising spend will grow by 4.8% in 2005 in line with Zenith's 5% forecast a year ago.
Zenith said the moderate growth reflects a tough comparison with 2004, which was buoyed by the presidential elections, summer Olympics and Euro 2004.
The figure is expected to increase to 5.9% in 2006, aided by mid-term elections and the football World Cup.
The report found a number of ad-growth hotspots around the world, with the US coming out on top as the largest contributor to global advertising growth. The US will account for 41-43% of global advertising between 2004 and 2008.
However, the most increased activity will be seen in Brazil, Russia, India, Indonesia and China. Taken together, these economies will supply 26% of global ad growth between 2004 and 2008.
By comparison, the UK, Germany, France, Italy and Spain, will see their share of the global ad market shrink from 19% to 17% over the same period.
The report singled out the internet as a driver of increased ad spend. Zenith said the internet will take 4.6% of advertising spend this year, rising to 6.4% in 2008. From 2005 to 2008, the internet is expected to create US$15.8bn worth of new ad spend.
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