The U.S. ad economy may be struggling but globally the media business is in a major boom, reflecting the growth of media economies of emerging nations such as China.

That's the finding of GroupM, the media and advertising conglomerate, in its latest ad spending forecast.

GroupM sees ad spending around the world growing by 7 percent next year, up from 6 percent in 2007, and it sees an ever-larger share of that spending taking place in countries that only a few years ago were considered media backwaters.

Indeed, it forecasts that in the coming year fully 5 percent of global ad spending will shift away from the developed nations to the emerging economies. This would be the largest shift ever, according to the author of the report, Adam Smith, who carries the title of futures director at GroupM.

The biggest growth engine by far, predicts Smith, will be China, which he believes will account for 21 percent of new spending. Russia and Brazil will account for 6 percent each, while India will claim 3 percent.

The forecast calls for U.S. ad spending to grow 3.7 percent next year, up from 2.8 percent growth in 2007 over 2006. That's somewhat slower than the 4.1 percent growth being forecast by ZenithOptimedia for next year, but even with Universal McCann's Robert Coen's forecast, released on Monday.

GroupM sees the strongest growth in 2008 in North Asia, at 18.7 percent, followed by the emerging economies of Europe at 17.8 percent. The slowest growth will be for North America at 3.9 percent.

The two forms of media to see the biggest gains will be TV and the internet, which the forecast figures to grow by 50 percent and 30 percent. While TV may be mature in the U.S., its growth has been robust in other parts of the world, especially the developing nations, over recent years.

Smith sees the internet gaining an increasing share of media budgets in the coming years, and he forecasts that in 2008 web spending will account for 10 percent of global ad budgets. Moreover, an increasing share will come from search, which he forecasts will account for as much as 70 percent, up from 50 percent in 2005.