With the global economy teetering, socked by one crisis after another, it's looking increasingly difficult for media, which typically hurl whip-like at the tail of the overall economy as it swings about.

These gyrations have already led to cutbacks in the outlook for ad spending, and now ZenithOptimedia is cutting back its forecast.

Forecasters at the giant media agency are chopping their outlook for global ad spending for both this year and next year as well.

Their latest revised forecast chops 2008 spending to 4.3 percent from the 6.6 percent it forecast in back in June. It's chopped its 2009 outlook to 4.0 percent from 6.0 percent, and it doesn't see growth picking up until 2010, when it's forecasting 6.1 percent growth.

ZenithOptimedia's outlook for the U.S. is far grimmer. It's pegging 2008 growth at 1.6 percent, down from the 3.4 percent it foresaw in June, and 2009 growth at 0.7 percent, down from 2.6 percent.

“These are fairly big revisions, more than we would expect for a normal quarterly revision. Forecasts for Western Europe and the U.S have effectively been cut in half,” says Jonathan Barnard, head of publications at ZenithOptimedia. "They have borne the brunt of the recent lack of confidence."

There is a positive side to the forecast, however. At this stage neither the global nor the U.S. forecasts slump into the negative.

“We are calling it a downturn but not an advertising recession. It is not a decline in advertising. It is a slowdown,” says Barnard.

He does not see the media economy going into the red in part because it didn’t soar to particularly lofty heights during the recent good times.

Unlike the previous downturns of 1990 and 2000, this one was not preceded by a period of extraordinary growth.

“If you look before 2001, the annual growth rate of the world’s ad economy was 10.4 percent in 2000 and 9.2 percent in 1999. We haven’t seen growth anywhere near that in the last few years,” says Barnard.

ZenithOptimedia expects that the worst of the effects of the credit crunch will be felt in the developed economies. While they have downgraded the forecasts for all regions in the developing world, the rates of growth still remain strong.

Another thing that is expected to remain strong is internet ad spending growth. The forecasters believe that the high level of measurability that the internet offers advertisers will continue to drive growth.

They forecast that that sector will grow by an average of 23 percent a year between 2007 and 2010 globally, to account for 13.8 percent of all world ad spend in 2010.

Even in the developed markets of the U.S. and Europe internet growth will be strong.

Looking specifically at the U.S., ZenithOptimedia forecasts that internet ad spending will grow 21 percent this year and 19 percent next.

Aside from the internet, ad spending in magazines and outdoor is also expected to grow next year in the U.S., at 2.5 percent and 7.1 percent, respectively. But newspaper spending is expected to drop 6 percent, while television is forecast to be down 1.3 percent.