Television ratings are already in a precarious state. What it doesn't need is a steep drop in quality content.

As the Writer's Guild of America continues to engage in contract talks with the Alliance of Motion Picture and Television Producers, the trade association that represents Hollywood's largest employers, it's instructive to consider the tenuous state of the television industry.

Of the top 25 shows on broadcast television, only two posted a ratings increase during the fall-winter season, according to Nielsen. The average ratings for the top 79 scripted shows on broadcast TV among those ages 18 to 49 was 13% lower than for the 2015-16 TV season.

Meanwhile, TV advertising grew 1% in 2016, fueled almost entirely by political ads, according to a Goldman Sachs report late last month. When political ads at cable-TV news networks are removed from the equation, the picture darkens. National advertising excluding cable-TV political fell by about 1.5%, a worrisome decline. 

Taken together, subscriptions to cable-TV services fell the most ever in 2016, according to media research group MoffettNathanson. The decline last year was 1.7%, or about 1.7 million subscribers. And while 2016 cable-TV ratings were bolstered by a chance in Nielsen methodology, MoffettNathanson is forecasting "sharp ratings declines" this year as more viewers spend more time at video-on-demand services led by Netflix (NFLX) - Get Report and Hulu not to mention free platforms like Facebook (FB) - Get Report and Snapchat (SNAP) - Get Report .

Which leads us to the Writer's Guild and the AMPTP, essentially the largest TV networks and movie studios.

The last time the Guild and the AMPTP were unable to agree on a new contract was back in 2007. At present, the Guild has voted to strike beginning May 1 if a new contract can't be signed.

Ten years ago, the Guild's strike forced broadcast and cable-TV networks to cut back in their offerings, pushing reruns and repeats as new content was reduced to a dribble. Viewing plummeted 21% during the first week of the 2007-08 strike, and through that entire season, dropped across all age groups, according to data compiled by Barclays in a report published on Wednesday.

The highest decline was among those aged 18 to 34, another worrisome data point. In hindsight, the Writer's Guild strike was one of many factors that led to Netflix's enormous growth. A comparatively young cable-TV industry benefited when the Guild struck in 1988, said Barclays analyst Kannan Venkateshwar.

This time around, a strike could have outsized impact on viewing habits. So-called over-the-top or internet-based platforms like Netflix and Amazon, while dependent on Guild writers, have a large library of original content, which in the case of Netflix includes shows produced in the U.K. 

"Given that inertia is the predominant driver of consumption patterns on television, forcing consumers to shift to Over-the-Top platform viewership could result in lasting changes in viewership patterns, given the proliferation of options today versus 2007," Venkateshwar said.

Advertisers, who are preparing for the industry's annual Upfronts gathering next month, may choose to hold back on purchases if the Guild strikes.

"Given the anemic growth rates for television advertising already, any uncertainty over the fall season is likely to force more advertisers to expand their allocations towards digital platforms," Barclays added. 

The Guild, which represents some 20,000 writers, argues that the industry has enjoyed great success in recent years. The largest media companies -- Disney (DIS) - Get Report , Comcast (CMCSA) - Get Report , 21st Century Fox (FOXA) - Get Report , Time Warner (TWX) , Viacom (VIAB) - Get Report and CBS (CBS) - Get Report -- generated a combined $51 billion in operating profit in 2016. Their top executives are among the best paid in all of U.S. business.

The industry, meanwhile, is said to be balking at the Guild's proposal for health coverage. Neither the AMPTP not the Guild were immediately available for comment. 

To be sure, television remains a good and profitable business. Yet there are cracks in the edifice. NFL viewing, which is the bedrock of networks such as CBS, reported an 8% drop in ratings with the average game being viewed by 16.5 million people compared to 17.9 million in 2015.

A strike by the men and women who write the shows that fuel profits at the country's largest media companies could throw a wrench in an industry already in the midst of enormous change.