As network executives gather in New York this week to unveil their fall schedules, the usual celebratory mood will likely be subdued. The 2007-08 TV season was pretty much a bust.

There were no new breakout hits, the writers' strike took viewer favorites away for months and when those shows returned, many viewers did not show up to watch them.

ABC, CBS, Fox and NBC had nearly 9 percent fewer viewers in April and May so far than during the same period a year ago, according to Nielsen Media Research.

Season-to-date ratings are also down year-to-year at ABC, CBS, NBC and The CW. Fox's ratings are generally flat or slightly improved.

TV's biggest hits are suffering, too. ABC's "Grey's Anatomy" was watched Thursday by almost 4 million fewer viewers than a year ago, reports have noted, and Fox's "American Idol" has suffered big ratings declines.

Broadcast network ratings have been declining year-to-year for many years, but "a confluence of several difficult dynamics came together" to make this a particularly bad season, said John Rash, senior vice president of media analysis at Campbell Mithun Advertising in Minneapolis.

Some of the factors include:

• Out of sight, out of mind: Some viewers simply got out of the habit of watching their favorite shows, particularly serialized dramas, and never came back after the strike ended and shows returned with new episodes.

"I kept saying this all along, you can't [tick off] a viewer these days," said Marc Berman, senior television analyst for Mediaweek and editor of The Programming Insider newsletter. "It's very easy for them to go elsewhere."

Several viewers responding to the Post-Gazette's annual "Keep or Cancel?'' poll cited the strike as the reason they've quit watching their favorite shows.

Allison Maksin, 27, of White Oak, said she didn't miss the shows she thought she couldn't live without, including "Grey's Anatomy," "Heroes" and "Gossip Girl."

"This ex-TV junkie is going to be more selective when choosing programming from now on," she said.

• DVR love: ABC warns in its ratings reports that the increase in DVR household penetration -- from a little more than 15 percent of homes a year ago to 24 percent currently -- can bring down overnight ratings, the basis for instant year-to-year comparisons.

But even after data comes in that accounts for DVR recordings that are played back within seven days after the telecasts are first available, ratings will still be down year to year.

"There are simply fewer people availing themselves of network television programs," Mr. Rash said.

The ability for viewers to catch up with shows online has eaten into prime-time ratings, too. Mr. Rash blames the programming, noting that if shows were better, more people would find a way to watch, whether live, online or on DVR.

"The bigger problem is not enough people choosing to watch in any form or fashion," he said.

With ratings down, networks are having to find other ways to decide which shows to renew or cancel for next season.

"The decisions networks make when they want to renew a show is not just about what the Nielsen numbers are," said Brad Adgate, senior vice president of research at New York's Horizon Media. "It's about how much are they downloaded or streamed online, how much do the DVDs sell. It's changed a little bit and takes a while to assess if a show is a hit."

• More options: With so many other ways for consumers to spend their free time -- watching TV shows on DVD, playing video games, interacting on social networking sites such as Facebook -- TV is being challenged on every front.

But from that perspective, TV is holding its own. People are not watching less television overall, just less broadcast network television.

"Television is an addictive medium and usage levels remain pretty much as they have been in recent years," Mr. Adgate said. "There's so much competition out there, especially from cable. They're getting better and better shows and more aggressive in their schedule."

With network TV ratings down, the amount advertisers pay for commercials on broadcast channels will likely follow, adding to pressures for the networks to make even more changes. A Merrill Lynch report published last week predicted upfront advertising sales -- commitments by advertisers to buy ads "up front,'' that is, before the start of the network TV season -- would decline 2 to 14 percent in the new season, according to TV Week.

With ratings down and a feeling that the TV business must change, the preview season is facing belt-tightening. Some series were ordered by networks without the production of a pilot -- test episodes filmed in advance of a series pickup. In other cases, producers shot a "presentation," a portion of a full pilot that will later be augmented with additional scenes if the show is greenlit to series.

With fewer clips to show advertisers in New York this week and more incentive than ever to save money, most networks are scaling down their dog-and-pony shows, which have traditionally begun in large Manhattan halls (e.g. Lincoln Center, Radio City Music Hall) and continued at big parties afterwards.

NBC skipped the upfront altogether, announcing its schedule a month ago and hosting a party for ad buyers at its NBC Experience store at 30 Rockefeller Plaza last night.

"CBS has gone from [having its party at] Tavern on the Green to inviting me to sit at a bar," Mr. Berman said.