If 100 million downloads can’t buy you the attention of big sponsors, what will? On Thursday, as the internet swooned about the return of “Serial,” it seemed like fans were excited that every single part of the hit podcast was back, including the ads.

The above tweet, a reference to an ad for Mailchimp that ran during the first season of “Serial,” speaks to how much goodwill and affection for the true-life-murder-mystery series had built up among its fans. Yet the fact that Mailchimp, Squarespace and Audible have returned as sponsors surprised industry observers, who'd expected “Serial” to draw some interest from heavyweight advertisers for its new season.   

It is fair to assume that both companies paid hefty amounts to return as the show’s sponsors. But podcasting will need to attract more advertiser interest if it wants to continue growing, and at the moment it appears that it is being held back by its antiquated advertising infrastructure and a lack of industrywide metrics.

“Where we are now in podcasting is like the '50s,” said Caitlin Thompson, the director of content at the podcast platform Acast.

Most digital media are supported by advertising that is very easy to track, count and sell at scale. Most podcasts, by comparison, are supported by ads read aloud by show hosts that are simply part of the sound file that a listener downloads onto their phone or computer. That makes it very difficult for advertisers to determine who is listening to the shows, and whether those people are even listening to the ads at all. 

Podcasting’s proponents will say that the host-read advertisements that constitute the medium’s bread and butter have a kind of timeless, quirky charm. And indeed, “Serial” fans’ love for the “mail kimp” does bear that out to an extent. But today, in an era when it is possible to target a specific ad to one specific person's smartphone, that level of sophistication won't cut it. 

“Coke's not going to buy a [podcast] ad if they can't tell they reached a 35-year-old woman in Connecticut at noon,” Thompson said.   

Without that surgical precision, which is transforming advertising in all industries, it won't matter that "Serial: Season 2" has the bigger, thornier story of Bowe Bergdahl to tell. It won't matter that show host Sarah Koenig has promised Bergdahl’s story will be told in a way that’s more ambitious, with things like 3D maps, video and interactive graphics.

podcastawareness_edison_1024 A graph shows awareness of the term "podcasting" is flat. Photo: Edison Research

Other challenges remain. Awareness of podcasting has essentially flatlined, with just under half of Americans aged 12 and up saying they know what a podcast is, according to Edison Research. Its relatively unsophisticated advertising infrastructure lacks the laser-like precision boasted by other digital ad formats. 

In every respect, podcasting has made major strides since “Serial” streaked across pop culture like a comet in 2014. Major broadcasters, including iHeartMedia and CBS, launched podcast operations this year, and large brands have begun to buy ads on networks like Midroll and Panoply.

“The idea that podcasting wasn't supposed to be an ancillary medium, but a legitimate medium, is something that Sarah Koenig deserves credit for,” Thompson said.