That's the finding of a new study by Magna, the giant media buying agency, after tracking shows for the past 10 seasons. Magna found that only 11 of 39 shows that got the most preseason hype went on to become hits. That's about the average hit rate for all new shows.

At the same time, a few shows that got no buzz in those years did go on to become hits, notably ABC’s “Lost” and Fox’s “House.”

Why the so-so success rate for buzzed-about shows?

For one, as the study points out, buzz gets people to tune into a show initially, but it's a one-shot deal. If the show isn't very good, those viewers won't come back in anywhere near their initial numbers.

“All the buzz and promotion in the world is only designed to get viewers to tune in once,” says Steve Sternberg, executive vice president of audience analysis at Magna. “After that, a show lives or dies on its own merits.”

But another important consideration is that buzz is hardly this spontaneous thing that builds on its own, sweeping from the internet to water coolers across the land. In reality, it's largely the work of network publicity departments, as just another promotional tool.

The difference between a show with heavy buzz and no buzz says more about where a network decided to put its promotional energies than anything else.

And like a lot of promotional efforts, they work if they get the viewers coming once. They can't save a show from failing.

Last season, NBC’s “Bionic Woman” suffered the fate of many buzzed-about shows. “Bionic” initially pulled big ratings but quickly faded. It isn’t returning for a second season.

Just last week, “90210” became the CW’s most-watched premiere ever. That show’s next few episodes will determine whether the sequel to Fox’s “Beverly Hills, 90210” lives up to its buzz.

Typically, it only takes viewers a few weeks to decide if a show deserves the hype it received.

And the networks sometimes just get it wrong in singling out shows they think will find an audience, such as NBC’s “Studio 60 on the Sunset Strip” two years ago. That show famously bombed.

Another factor working against heavily buzzed shows is that they are often the shows the network thinks of as edgy, but those shows often fall flat with the average television viewer, explains Sternberg.

“Buzzed-about shows so often fail because most of them have been younger-skewing series while the typical broadcast viewer is older,” he says. “You seldom see CBS series get the most buzz but, over the past five seasons, they have developed the most hits.”

This season, Fox takes the crown for working the hardest to create buzz for “Fringe,” which premiered last night. Fox’s marketing team has rolled out a number of stunts, like putting live cows onto the streets of Manhattan, to build up buzz for the show.

Last season, seven shows generated the most buzz, including Fox’s “Back to You,” NBC’s “Bionic” and CBS’s “Cane.” None of these are back this season.

ABC’s “Pushing Daisies,” NBC’s “Chuck” and the CW’s “Reaper” and “Gossip Girl” are back, although partly because the networks are giving some shows a do-over after last season was disrupted by the writers’ strike.

Of five buzzed-about shows in 2006, only two made it – ABC’s “Ugly Betty” and NBC’s “Heroes.” Of the two most-buzzed-about shows in 2005, both NBC’s “The Office” and UPN’s “Everybody Hates Chris” remain on the air, with “Chris” now on the CW.

More often, the success rate is far lower.

In 2004, five of six buzzed shows failed, including NBC’s “Joey” and the WB’s “Jack & Bobby.” And in 2003, all three buzzed-about shows bombed, most memorably NBC’s “Coupling.”