Economic shocks from political turmoil in the Middle East and the earthquake in Japan have knocked about $2.4 billion off this year's global advertising expenditure, leading media buyer ZenithOptimedia estimates.

The Publicis-owned agency cut its growth forecast on Monday for 2011 advertising spend to 4.6 percent from the 4.2 per cent it had predicted in December.

In Egypt, by far the largest ad market to be caught up in the uprisings, there was almost no TV advertising during the revolution, and advertisers were very careful about the content and placement of their messages in the aftermath, it said.

In Japan, the world's second-biggest ad market, broadcasters replaced almost all ad slots with public-service announcements for weeks, and ZenithOptimedia said blackouts and distribution problems would hinder media consumption for months to come.

"We do not expect these shocks to derail the global recovery in the long term, however. We expect some of the missing advertising to reappear later in the year, followed by strong growth in these markets in 2012," it said.

ZenithOptimedia raised its 2012 forecast, saying it now expected the market to grow by 5.8 per cent to $498 billion. It had previously forecast 5.2 percent growth.

The United States will remain far and away the world's biggest advertising market through its forecast period to 2013, ZenithOptimedia said, but it predicted that Brazil would overtake France to become the sixth biggest this year.

It repeated its forecast that China would overtake Germany to become number three, also in 2011, while Britain would remain in fifth place.

ZenithOptimedia also predicted that the Internet would overtake newspapers to become the second most popular advertising medium behind television in 2013. – Reuters