Two IAB Studies Disagree About Podcast Ad Growth. Which One Is Right?

What do the two studies actually say?

In April 2026 the Interactive Advertising Bureau published its Internet Advertising Revenue Report for full-year 2025, prepared with PwC Advisory Services. It put United States podcast advertising revenue at $2.862 billion, a 17.6% increase on 2024, inside a digital audio category worth $8.4 billion that grew 10.2% from $7.6 billion.

In January 2026 the same trade body published its 2026 Outlook Study, built from interviews with more than 200 brands and agency buyers. That study reported podcast advertising growth of 7.9% for 2025 and forecast 9.6% for 2026.

Both describe United States podcast advertising in 2025. They differ by 9.7 percentage points.

It is worth being precise about what each document is called, because the two are routinely quoted as though they were one. The April publication is the Internet Advertising Revenue Report, an annual accounting of the whole United States internet advertising market in which podcasting is one line. The January publication is the Outlook Study, a forward-looking survey of buyer intent in which podcasting is one category among the media those buyers plan to purchase.

Neither is a correction of the other and neither was withdrawn. Both remain published, which means anyone citing IAB data on podcast advertising in 2025 can, in good faith, cite a figure roughly double or roughly half of what someone else is citing from the same organisation.

The size of the gap is easier to grasp in money than in percentages. Applied to a 2024 base of roughly $2.43 billion, a 17.6% increase produces the $2.862 billion the revenue report states. A 7.9% increase on the same base would have produced about $2.62 billion. The difference between the two accounts of the same year is on the order of a quarter of a billion dollars, which is larger than several of the categories the same report tracks separately.

Why would the same organisation publish two different numbers?

Because they measure different things. The revenue report is a supply-side collection: PwC gathers reported revenue from the companies that sell podcast advertising and supplements it with public filings. The Outlook Study is a demand-side survey: it asks buyers what they spent and expect to spend.

Those two populations do not see the same market. A seller's revenue includes every dollar booked, including from advertisers too small to appear in a survey of 200 large brands and agencies. A buyer survey captures the intentions of the biggest spenders, weighted toward the agency-mediated part of the market. A category growing fastest among smaller direct advertisers would show exactly this pattern: strong in the seller collection, weaker in the buyer survey.

Timing compounds it. The Outlook Study was published on 29 January 2026, before 2025 was fully closed and reported. The revenue report was published on 16 April 2026 with the year complete. A January figure for the year just ended is an estimate; an April one is a count of what was reported.

A third difference is what counts as podcast advertising at all. A revenue collection captures what sellers booked under that heading, including host-read endorsements, programmatic inventory sold against audio streams, branded series commissioned directly, and sponsorship of live events attached to shows. A buyer survey captures what a media planner calls podcast spend, which is typically the line in a plan headed podcast. Money spent on a branded series produced by a podcast studio may appear in one and as content production in the other.

None of these explanations requires anyone to have made an error. They are the ordinary consequence of measuring a market from two ends. The error is in quoting either figure without saying which end it came from.

There is also a question of who answers a buyer survey. The 200-plus respondents are brands and agency buyers, which is a population selected for scale: the advertisers large enough to have a media buying function and to be worth surveying. Podcast advertising's distinctive feature as a category is the weight of direct-response spending from advertisers that have no agency at all, and those advertisers are structurally under-represented in any buyer panel.

How large is podcast advertising relative to everything else?

Podcast advertising is about 34% of United States digital audio advertising, which is itself a small part of internet advertising. In the same 2025 data, digital audio grew 10.2%, ahead of display at 9.8%, behind total internet advertising at 13.9%, and far behind digital video at 25.4% and social at 32.6%.

This is the context that most podcast advertising coverage omits. The format is growing, and it is growing more slowly than the formats it is often compared against. A report that podcast advertising grew 17.6% reads as a boom until it is set beside social media's 32.6% in the same year and the same report.

The comparison also reframes what podcast advertising is competing for. Growth capital in advertising follows measurement, and the formats growing fastest in this data are the ones where attribution is tightest: social and video platforms that can observe a click, a view and a conversion inside one system. Podcasting's measurement problem is the reverse, since much of its consumption happens in applications that report a download rather than an outcome.

That is the structural reason the category can be simultaneously the fastest-growing line inside digital audio and a slower-growing line than digital media as a whole. It is winning its own category and losing the wider competition for budget, and both facts sit in the same table of the same report.

Which number should be used, and for what?

For the size of the market, the revenue report is the better instrument, because it counts money that was actually booked rather than money buyers recall or anticipate spending. For the direction of large-advertiser intent, the Outlook Study is the better instrument, because that is precisely what it asks.

Neither should be described as audited. PwC's stated position is that it collects the information from the companies selling the advertising and from public filings, does not audit it, and expresses no opinion or assurance on it. That is a standard arrangement for industry revenue reporting and it is not the same as an audit, a distinction routinely lost when these figures are quoted.

There is a further definitional caveat that affects the size figure specifically. The IAB and PwC note that their podcast numbers reflect the traditional, audio-based definition of the medium, while roughly 71% of United States podcast creators now produce video versions. Revenue attached to video podcast inventory may be counted in video rather than podcast, which would understate the category by an amount neither body quantifies.

For a business deciding where to spend, the more useful question than which figure is right is which figure is load-bearing. If the decision is whether a category is large enough to be worth entering, the revenue report answers it: $2.862 billion is a real market. If the decision is whether large advertisers are about to bid up the price of inventory, the Outlook Study answers it better, and its answer is more cautious.

The two studies disagree least about direction. Both report growth; both report it continuing into 2026. The disagreement is entirely about rate, and rate is the thing most often quoted and least often sourced.

One practical test separates the two instruments cleanly. If a figure is being used to argue that a market exists and is worth entering, it should come from the revenue side, because that is a record of money that changed hands. If a figure is being used to argue about what will happen next year, it should come from the buyer side, because intent is the only thing that forecasts spending and sellers cannot report revenue that has not yet been booked.

Methodology and limitations

This report compares two publications of the Interactive Advertising Bureau: the Internet Advertising Revenue Report for full-year 2025, prepared with PwC Advisory Services and published 16 April 2026, and the 2026 Outlook Study published 29 January 2026 and based on more than 200 brands and agency buyers. Growth rates by format are taken from the former. Three limits apply. First, PwC collects revenue from sellers and public filings and does not audit it or provide assurance on it; no figure here is an audited account. Second, the Outlook Study's figures are survey responses about spending intentions, subject to recall error and to the composition of its 200-plus respondents, which is not published in the coverage reviewed. Third, the podcast revenue definition is audio-based while most creators now produce video, so the category total is understated by an unquantified amount. Where the two studies conflict, both figures are printed rather than one being selected.

Conclusion

Two IAB publications give podcast advertising growth in 2025 as 17.6% and as 7.9%. Neither is wrong. One counts revenue reported by sellers after the year closed; the other surveys large buyers before it did. The useful discipline is to state which instrument a number came from whenever it is quoted, because the same category can be described as growing at twice the rate of all internet advertising or at just over half of it, depending on which IAB study is open. What neither supports is the word audited, and what both understate is a category being measured as audio while it migrates to video.

Frequently Asked Questions

Sources

1. trade body Interactive Advertising Bureau and PwC Advisory Services, 2026. Internet Advertising Revenue Report, Full Year 2025, published 16 April 2026.
2. trade body Interactive Advertising Bureau, 2026. 2026 Outlook Study, published 29 January 2026, based on more than 200 brands and agency buyers.
3. trade press Radio Ink, 2026. “IAB: Digital Audio Grew 10% In 2025 as Podcasts Near $3B”, 16 April 2026.
4. trade press Inside Radio, 2026. “IAB Forecasts Podcast Ad Growth To Accelerate In 2026”, reporting the IAB 2026 Outlook Study.