The reason is simple: Radio bested online and television when it came to delivering a specific audience.
The campaign was the 7/15/15 Amazon Prime Day.
The prime target audience was 18-34.
Amazon bought network television and an assortment of cable channels, including many younger skewing ones. But it did the poorest job of delivering the demo.
Radio ads, however, targeted to Top 40, Country, AC and Classic Rock stations, did the best.
Here are the audience breakdowns for each medium.
Bouvard notes that dollar for dollar, radio delivered 40 cents, online 35 cents and TV 27 cents.
Radio also delivered a far greater recall per dollar value, $100,000 per awareness point versus $177,000 for TV.