Podcast adspend hit $479.1m in the United States last year following annual growth of 53%, and should top $1bn by 2021, according to a report by the Interactive Advertising Bureau (IAB), the trade body, and PwC, the professional services firm.

Using a mix of self-reported ad revenue from 22 companies in the podcasting space and wider market sizing, the IAB/PwC analysis struck a highly optimistic note for the category.

The total ad expenditure generated by this audio channel is projected to come in at $678.7m in 2019, they reported, before reaching $863.4m in 2020 and surpassing the $1bn threshold in 2021.

Anna Bager, evp/industry initiatives at the IAB, suggested that the expanding slate of listening environments – which runs from desktop to smartphones and voice-activated speakers – is a key driver of this momentum.

“Today’s technology has created an audio-first environment where audio is the preferred interaction – and consumers have put podcasts front-and-center,” she said.

“Podcast storytelling is deeply engaging and provides marketers with a brand safe environment that enhances the appeal to advertisers.”

One notable trend identified by the IAB/PwC report was the growing use of podcast ads as a brand-building tool, as 38.2% of revenue came from brand awareness ads in 2018, compared with 29.2% in 2017.

Branded content registered an uptick from 6.5% to 10.1% on the same metric. Direct-response ads, by contrast, witnessed a decline in their revenue share from 64.2% to 51.6% year on year.

Sixty-second ads were the most popular format, comprising 30% of inventory sales, ahead of 90-second offerings on 27%. Fifteen-second executions posted 23% here, with 30-second spots on 19%.

News, politics and current affairs was the podcast content category attracting the most spend, beating comedy, business, and then education. Together with arts and entertainment – which saw a dip in demand last year – these five genres took 65.7% of ad revenue.

Direct-to-consumer retailers were the biggest spenders, followed by financial-services providers, business-to-business firms, arts and entertainment brands, and telcos – with the last of these industries logging a 77.5% increase in expenditure.

“The steady climb in revenues for the podcast ad market underscores the value of the platform’s flexibility and reach," David Silverman, a partner at PwC US, said.

“Consumers are listening to podcasts wherever and whenever – from their morning workout to their evening commute – making it appealing to brands that want to reach today’s audiences.”

Sourced from IAB; additional content by WARC staff