Listen to this: The podcast advertising biz is continuing its upward trajectory — with U.S. ad sales expected to grow 47% this year to $2.13 billion, according to a new forecast from trade group IAB and PwC.

That’s actually a deceleration from last year. The sector hit $1.45 billion in 2021, representing 72% annual growth, according to the report. In 2021, U.S. podcast advertising revenue grew twice as fast as the total internet advertising market, which was up 35% last year, according to the 2021 PwC/IAB Internet Advertising Revenue Report.

Still, U.S. podcast advertising revenue is poised to continue double-digit growth, growing more than 100% over the next two years to an estimated $4.2 billion in 2024, per the report.

According to the latest IAB/PwC podcast report, three key factors are driving podcast ad revenue growth: the ongoing increase in listeners and content; increased use of automated ad tech, as ad revenue served via dynamic ad insertion (DAI) has almost doubled in two years to take 84% share in 2021 (versus ads embedded in podcast audio); and growth of ad spending in categories that historically had lower spend volumes like sports and true crime.

The IAB/PwC 2021 U.S. Podcast Advertising Revenue study’s lead sponsor is SXM Media, the ad-sales arm of SiriusXM, along with AdLarge Media, AdsWizz, Backtracks, Cumulus Podcast Network, iHeartMedia, LAist Studios, Market Enginuity, NPR, Spotify, Slate and Amazon’s Wondery.

“Everything right now is aligned to drive growth,” said Chris Bruderle, IAB’s VP of research and insights. “There’s more engaging and diverse podcast content than ever, and that is translating into larger, more attractive audiences. But more than anything, podcasting has proven that it can deliver beyond direct-to-consumer advertising to support brand-building and drive business outcomes.”

The report was released ahead of the online-only IAB Podcast Upfront 2022 marketing event, which runs May 10-12.

The sixth annual IAB U.S. Podcast Advertising Revenue study, as in years past, is based on an online survey sent to “leading podcast industry experts” fielded in March. It also incorporates market-sizing estimates for the U.S. inclusive of non-survey participating companies.