Eight years on, we may have an answer.

Reality shows on broadcast networks are in a serious slump, with virtually every returning show down from last season, and none of the new reality shows has become a hit. ABC’s “Opportunity Knocks” is already on hiatus.

This doesn't appear to be a temporary slump either. The only question is whether the genre is headed for a gentle slide or a fast tumble.

The genre is suffering for a number of reasons but key is that reality has become predictable, even a bit boring. The formats are now few and familiar, typically competitions pitting teams against one another, and the genre’s biggest hits, like Fox’s “American Idol,” ABC’s “Dancing with the Stars” and CBS’s “The Amazing Race,” have been on for years.

“These shows are like scripted shows. After a while there’s some fatigue,” says Brad Adgate, senior vice president and corporate research director at Horizon.

“Rather than sit through another season of an unscripted show, people want to see what else is on. And there’s more competition than ever before. Cable is just littered with these shows.”

Says Maureen Ryan, Chicago Tribune’s TV critic: “The great thing about reality in its heyday was that you’d get these people that would make you think, ‘Wow, I can’t believe this person is acting that way. Now people have seen ‘Amazing Race’ and ‘Survivor’ dozens of times and they know how it works. The novelty has worn off.”

Every returning broadcast unscripted show is down from last season, from 7 percent (“Dancing’s” results show) to 38 percent (“Deal or No Deal”) among total viewers, based on live-plus-same-day ratings, according to an analysis of Nielsen ratings by Horizon.

The only exception is NBC’s “Biggest Loser,” which has made a few tweaks the past couple of years, including this year’s family edition. It’s up nearly 7 percent.

Certainly some of that reflects the overall slide in ratings for all the broadcast networks this season, but the bigger part is the weaker performance of the genre. Other genres are either posting ratings increases, like newsmagazines, or they’re a mixed bag with at least some shows posting improved ratings.

Another possible factor behind reality's decline is the rough economy and presidential elections, which could be diverting viewers’ attention. That's suggested in the ratings of the newsmagazines. CBS’s “60 Minutes” is up 12 percent over last season. ABC’s “20/20” is up 8 percent, and CBS’s “48 Hours Mystery” is slightly up.

But as Adgate suggests the real issue is that reality shows are ubiquitous on cable, where many networks have lineups almost entirely filled with reality shows.

Indeed, as a genre reality seems a more natural fit for cable, where the networks can afford to experiment with new approaches to the genre and be pleased if they attract an audience and the attention of critics.

Some cable networks have generated a lot of attention for newer reality subgenres, notes Bob Thompson, director of the Bleier Center for Television and Popular Culture at Syracuse University, including documentary-style shows like History’s hit “Ice Road Truckers” and Discovery Channel’s “Dirty Jobs.”

“I think reality will be around forever,” he says. “But we’re in a phase, like we were a few years ago with sitcoms, where all the shows are kind of old. A lot of the exciting reality shows that people are talking about are on cable. There hasn’t been a big new reality show [on broadcast] in quite a while.”