AMC Networks' (AMCX -0.44%) The Walking Dead continues to be the top show on cable, and much like its zombies, the franchise...just...doesn't...stop. There are video games, comic books, novels, action figures, a talk show, and even a companion spinoff in the works. Will it succeed where others have failed?
In late 2011, 24/7 Wall Street and NBC News estimated the size of the "zombie economy" to be nearly $6 billion. Blockbuster movies like 28 Days Later and Zombieland accounted for about half of this figure, while the remaining dollars were split mostly between games, comics, and television. Assuming reasonable growth over the past two years, aided by World War Z, and Dead's rising popularity -- season four viewership is double that of season two -- $7 billion isn't out of the question.

Courtesy of AMC.

Sources: Television Obscurities, Business Insider, IMDb. Because majority of historical ratings data is unavailable, shows are designated as Hits (Green) or Flops (Red). A show flops because it either: (a) generates significantly less viewership than the original, (b) is canceled after its first season, or most likely, (c) both.
One point is abundantly clear when looking at the data: The majority of past spinoffs were comedies, and of those remaining, almost all were legal and romantic dramas. The Walking Dead will be the first survival horror to join this club.
In addition to novelty, AMC's companion series is in a good position to succeed because it will debut while its primary show is still on the air. In recent history, the majority of spinoffs in this position were hits -- Private Practice, CSI: New York, CSI: Miami, Stargate Atlantis, and NCIS -- and it makes sense. Viewers are more likely to support a spinoff if they're still watching the original. Many of TV's biggest flops, like Joey and The Golden Palace, failed in part because they didn't follow this strategy.
The bottom line
It's easy to understand why fans are excited about The Walking Dead's spinoff, and considering recent history, AMC should be psyched too. No matter what time slot the series is given, it will be the second most popular show on cable TV if it can just draw half of Dead's current audience.
The zombie-filled world Robert Kirkman created will only get bigger with time, and that's good news for everyone, except maybe its original characters. I don't know if Daryl, Michonne, and the rest of Rick's crew can survive beyond 10 seasons.