"ZenithOptimedia predicts that Internet ad spend will grow 28.2% in 2007, while the rest of the market grows 3.7%," reads the agency's report. "We now expect the Internet to overtake radio in 2008, a year earlier than in our last forecast. 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."

The report notes that the Internet already garners more than a 10% share of ad spending in three markets - Norway, Sweden and the U.K. - and by 2009 that margin is expected to expand to 11 major markets, including the U.S., Australia, Canada, Denmark, Israel, Japan, Norway, South Korea, Sweden, Taiwan, the U.K.

After online, cinema and outdoor media are the fastest growing advertising media, and are projected to outpace the overall advertising economy through 2009.

In its last report issued early this year, ZenithOptimedia signaled concerns that TV was poised to enter its first ever period of protracted ad market share loss, but in today's report, the agency notes that "demand has picked up" for TV advertising inventory worldwide, and now expects "television's share of global ad expenditure to be just 0.2 percentage points lower in 2009 than it was in 2005."

The agency meanwhile downgraded its outlook for newspapers and magazine publishers due to advertisers shifting budgets from print to online media. That trend is expected to be most pronounced in the U.S., where ZenithOptimedia now predicts "no growth" in U.S. newspaper ad spending, and "less growth from magazines than we forecast in December."

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