Sean Murray, left, and Mark Harmon in a scene from "NCIS," which has never won an Emmy but last year became the most popular show in the world with 57.6 million viewers in 66 countries. (Cliff Lipson/AP)

As television gets back into full swing this fall, several premieres will hog the attention of critics and social media chatter.

“NCIS” won’t be one of them. The military crime drama on CBS has never won an Emmy. Its cast, led by 1980s TV fixture Mark Harmon, rarely makes celebrity gossip sites.

And yet the primetime show, where a motley team of investigators set out to solve military crimes, is one of the most popular and profitable programs on TV. Its premiere this week topped Tuesday’s ratings and the show is on the way to stretching its five-year streak as the most-watched drama on television with an average audience of 20 million people, according to Nielsen. Last year, it became the most popular show in the world with 57.6 million viewers in 66 countries.

Now in its 12th season and with two spinoffs, the show is granting CBS what analysts describe as the “NCIS effect,” becoming an almost indestructible franchise for the network — a phenomenon that only a few juggernauts, such as “Murder She Wrote” and “E.R.,” have experienced. Its staying power is in its formulaic approach and vast appeal among older viewers, who spend the most time in front of TVs; the median viewer of CBS is 58.7 years old. And because each episode is self-contained — no need to watch entire seasons to get the narrative arc — CBS is able to easily syndicate the show.

“ ‘NCIS’ is the jewel in the family crown,” CBS chief executive Leslie Moonves said in a recent interview. “We don’t see this losing popularity any time soon.”

TV shows that thrived despite criticism

“NCIS” is proof that even years after the rise of Netflix and YouTube, traditional television is thriving. Americans are watching more broadcast and cable television than ever — five hours a day — and they are simply adding more time with videos by watching online. Among all its competitors, CBS has exploited that traditional audience best, making it the most watched of the big networks for 11 of the past 12 seasons.

“Although new digital entrants destroyed the revenue models and market capitalizations of newspapers, music and yellow pages, TV content producers have largely benefited from new digital entrants,” said Laura Martin, a media analyst at the investment firm Needham Co.

That will likely change, analysts say, because younger viewers are spending more time on mobile devices than in front of the living room television set. CBS and other broadcast networks are in danger as consumers rethink expensive subscriptions for cable, where networks make a huge portion of their revenues from licensing fees and advertising. CBS is under pressure to find another franchise hit to fill the void when the popularity of “NCIS” fades.

But for now, CBS and other television programmers such as Time Warner and Viacom are riding high off the stubbornly persistent cable model. CBS’s stock increased 30 percent in 2013 and has held steady for much of this year. The company’s consistent growth has rewarded its chief executive Leslie Moonves with a compensation package of $66.9 million last year, one of the highest corporate paydays in the nation. CBS’s revenue grew 8 percent in 2013 to $15.28 billion.

“ ‘NCIS’ may not get the buzz that shows like ‘Orange Is the New Black’ get, but for CBS it hits every window for exploitation,” said David Bank, a media analyst for investment firm RBC Capital Markets.

When a new “NCIS” season airs, the network gets money from advertisers on broadcast, retransmission fees from cable and satellite providers, and revenue from online services such as Amazon Instant Video. In contrast, Netflix’s “Orange is the New Black” is only available to Netflix subscribers.

“CBS gets the whole cradle-to-grave experience, which is where the money is,” Bank said.

CBS launched “NCIS” in September 2003 with a simple formula: By the end of each episode, an investigation would be solved, and its diverse cast would provide light-hearted humor along the way.

With Mark Harmon playing the older, handsome lead agent, Leroy Jethro Gibbs, the series began in the Naval Criminal Investigative Service office in Washington. In 2009, the spinoff “NCIS: Los Angeles” brought in a new cast to explore similar crimes on the West Coast. This week, executive producer Harmon introduced another spinoff with the same format: “NCIS: New Orleans.”

All three shows premiere this week and next, taking top prime-time spots. The buildup has been huge on radio, billboards, on-air during other CBS shows and online. “NCIS” has 18 million Facebook fans.

In “NCIS: New Orleans,” the format is full of familiar TV types. The group of agents includes a handsome, young investigator who “plays hard but works harder,” and a female agent whose tainted past brings her to New Orleans for a “fresh start,” according to CBS’s show description on its Web site. As with Harmon, “NCIS: New Orleans” has its own older lead investigator, Special Agent Dwayne Pride, played by Scott Bakula, of “Star Trek: Enterprise” and “Quantum Leap” fame.

Like the original show and “NCIS: Los Angeles,” the new spinoff requires little commitment. A fan of AMC’s “Breaking Bad” has to watch dozens of episodes to finally figure out what happens to Walter White, but an “NCIS” fan can dip in and out of the show at will.

It’s a convenience that appeals to many fans — perfect to watch while on the treadmill or while folding laundry, analysts say.

Those elements make for a show that appeals particularly to older audiences. The median age of an “NCIS” viewer is 60, and the show is most popular in Louisville; Pittsburgh; Dayton, Ohio; and Kansas City, Mo., according to CBS. Overseas, it’s most popular in Canada, France, Germany, Sweden and Italy.

There are few shows with such reliable big-audience appeal. Just a few episodes into the “NCIS: Los Angeles” debut in 2009, cable’s USA Network bought the syndication rights to 12 years of the show. It is the longest syndication deal in the history of television.

Much of CBS’s success is credited to its chief executive, who has been a guard of the old television model where money is made in big live events such as NFL games and by selling content to cable and satellite firms. In a recent conference call with investors, CBS chairman Sumner Redstone introduced Moonves as a “super- genius.”

Moonves came to CBS in 1995 and is in many ways a throwback to an earlier era of TV. In his Los Angeles and New York offices, he uses magnetic tiles on a board to arrange the schedule of CBS shows by hand.

The 64-year-old says that as long as the company focuses on producing popular content, it doesn’t matter what distribution platforms emerge. In 2008, he declined to back Hulu, the online platform for Walt Disney’s ABC, NBC Universal and Fox. Analysts say that decision has given CBS more flexibility in negotiating terms with other online partners.

Lately, Moonves has been more experimental in putting shows online, with a deal to produce 26 episodes of “Under the Dome” for Amazon Prime Instant Video.

But he’s wary of moving too quickly. Netflix and HBO attract huge audiences who have become accustomed to viewing entire series online at once, but Moonves said he’s cautious about eating into the company’s advertising profits.

“Bingeing hasn’t become the be-all and end-all,” Moonves said during the Goldman Sachs Investor conference in New York this month. “It’s a very cool thing to do, I get it. We want to be careful. Our bread and butter is still advertising.”

Instead, Moonves has aggressively grown revenues by pushing for higher cable and satellite fees. Those demands have led to bitter feuds with cable partners, including a prolonged dispute last fall with Time Warner Cable that led to blackouts for CBS shows.

That’s also why Moonves took a lead in fighting Aereo, an online video distributor that lifted local television stations’ signals to stream them to its own subscribers. In June, the Supreme Court agreed with CBS, NBC Universal, PBS, Fox and ABC that Aereo violated copyright laws.

That decision safeguarded Moonves’s plans to grow retransmission fees from nearly nothing four years ago to $1 billion in 2017 and $2 billion in 2020. And he’s betting live sports will be a bigger part of the company’s revenue growth. CBS paid the NFL $275  million to air eight Thursday night games this season.

But in some ways, the strategy behind CBS’s success is like plugging holes in a dam, some analysts say.

A great debate underway is whether young audiences will buy into cable packages when they become adults. Some Silicon Valley investors have funded online video producers such as Vice and Buzzfeed that they believe are more appealing to millennials.

CBS has found a younger, but smaller, audience online. But even there, the median age for an “NCIS” fan is 47 years old.

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