“S-Town,” the latest narrative podcast from the producers of “Serial,” has already outdone its predecessor.

In its first week of release, listeners downloaded episodes of “S-Town” 16 million times. It took eight weeks for the first season of “Serial” to reach that number, and four weeks for the second season to hit it, according to numbers provided by Serial Productions. “S-Town” is the first series released under the Serial Productions banner — the outfit is helmed by the makers of “Serial” and “This American Life” — and by podcast standards, it’s a blockbuster.

“This is certainly the fastest that a podcast has accrued that big of an audience, no matter how you cut it,” said Nick Quah, who analyzes the podcast business in his weekly industry newsletter Hot Pod. In just over a week, “S-Town” has attracted 1.8 million subscribers to its podcast feed. “No one’s done that,” Mr. Quah said.

Reliable podcast data for the entire industry is hard to come by, as publishers in the still-developing medium are notoriously shy about revealing the size of their audiences, and no third-party metric exists across all podcast download platforms. Even Serial Productions’ willingness to talk numbers speaks to its dominance in the podcasting space.