It turns out the NFL, sports' modern-day television ratings king, is not unbeatable.

During the fall, the super popular AMC drama The Walking Dead scored higher ratings in the all-important 18-to-49-year-old demographic in five out of eight weeks while going against NBC's Sunday Night Football.

Even though the NFL's Sunday night contests haven't all been thrillers, this is a remarkable accomplishment for AMC.

Sports Illustrated media writer Richard Deitsch put the show's feat into perspective in his column this week:

"It’s a remarkable television feat given that the NFL simply does not get out-rated on Sundays, and it makes you wonder if other networks can glean something from AMC, short of creating a show about a zombie apocalypse."

Additionally, The Walking Dead will end ESPN's 27-year run of having the most watched cable series, a streak that started when it carried Sunday Night Football and then shifted to Monday Night Football in 2006.

AMC president Charlie Collier told Deitsch that his network's feat is attributable to a year-round marketing effort, which includes the show's strong presence at conventions like Comic Con and constant social media postings. Just like how the NFL uses the Combine and the Draft to stoke offseason interest, AMC knows it must keep pushing its product throughout the year.

​"We don’t per se look at The Walking Dead in comparison to the NFL," Collier told Deitsch. "What we are really trying to do is create a fan experience and an event each week that moves and engages every viewer. For fans of The Walking Dead, the show is like their favorite team playing a home game on national TV every week."

AMC cleverly split the fifth season of "The Walking Dead" into two parts. The first half ended a few weeks ago and the second half picks up in February. There's a reason for the timing; while the show can compete with the NFL during the regular season, the playoffs are another beast. So the show proved its muscle this fall and will likely score enormous ratings in the winter when it isn't competing with football.

It should be noted, furthermore, that if time-shifted viewing (people who watch the program on DVR) is included in the ratings, "The Walking Dead" would have beaten the NFL each week.

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