US Podcasting ad revenue exceeded $300m in 2017

"U.S. podcast ad revenue hit an estimated $314 million in 2017, an 86% increase from $169 million in 2016, according to findings from the Interactive Advertising Bureau (IAB) and PwC made available to Marketing Dive. The report, the IAB's second annual Podcast Revenue Study, forecasts that podcast revenue will reach $659 million by 2020, a 110% increase from 2017.
The preferred type of podcast ad was host-read, which made up two-thirds of podcast ads in 2017. Direct response ads accounted for 64.2% of campaign revenue, with brand awareness ads at 29.2%. Ads integrated or edited into programming made up 58% of the podcast ad inventory in 2017, up from 43.6% in the previous year."

Source:  Marketing Dive, 12th June 2018