On of the largest television events of the year drew 98.2 million people on CBS, the lowest since 97.5 million in 2008 and the fourth straight year of decline.
Nielsen said overall, the game drew a 44.9 rating. It was the lowest scoring game in Super Bowl history, with a combined three field goals and a touchdown in the Patriots 13-3 win over the Rams Sunday.
Nielsen said 67 percent of U.S. homes with televisions in use were tuned into the Super Bowl, down from 68 percent a year ago. Ratings peaked with the 2015 Super Bowl, between the Patriots and Seattle Seahawks, when 114.4 million people tuned in.
Despite the decline, ad prices still increased. A 30-second spot cost $5.25 million this year, up from $5.2 million for NBC's Super Bowl LII broadcast last year. CBS raked in $382 million in advertising revenue, the third-largest amount in the 53-year history of the Super Bowl.
The low viewership could leave big spenders like Anheuser-Busch, Coca-Cola, Amazon, Pepsi, T-Mobile and Hulu with regret.
There's "no correlation between viewership and pricing. It's more linked to the economy," Dan Granger, CEO of ad agency Oxford Road, said.
But Super Bowl advertisers do have provisions in their contracts so if ratings are down, they can get prime time slots on favorable terms to compensate, said Allen Adamson, co-founder of branding firm Metaforce.
"The Super Bowl is still valuable to so many outlets," Adamson said. "There's still a long list of people who want to advertise. That's because there are so few opportunities to talk to 100 million people at once."