The latest "Advertising Expenditure Forecast," published by ZenithOptimedia, predicts that Internet advertising will take more than 10% of all ad expenditure in two markets this year: in the UK, where it will account for 12.9% of total expenditures, and Sweden, where it will take 10.5%.

This will be the first time that Internet advertising has enjoyed a double-digit share anywhere in the world.

By 2008, ZenithOptimedia expects six other online ad markets to crack the double-digit market share barrier: Australia, Israel, Japan, Norway, South Korea and Taiwan.

As a result of this robust growth, the firm has upgraded its worldwide Internet advertising forecast, and now expects expenditures to grow 84% between 2005 and 2008.

According to ZenithOptimedia, the Internet’s share of global ad expenditure was 4.7% in 2005, and it will grow to 5.7% in 2006 and 7.3% in 2008. At that rate of growth, the Internet’s share of advertising should reach double digits worldwide by 2011.

Worldwide Internet ad expenditures will grow from $18.6 billion last year to over $24 billion this year, $29 billion in 2007 and $34 billion in 2008.

In addition, the Internet will overtake outdoor advertising’s share of total ad spending this year, and it is rapidly closing in on radio. ZenithOptimedia predicts the gap between the Internet’s share and radio’s share will narrow from 3.9 percentage points in 2005 to 0.7 points in 2008.

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