Viewership for Netflix's 'Fuller House' season 2 is tanking, according to a research company

Netflix comedy "Fuller House" is beginning to show some cracks in its foundation. Its recent season-two premiere ratings are reportedly tanking.

According to SymphonyAM, which has an app that listens to sounds from users' televisions and takes that data to extrapolate viewership, the premiere ratings for "Fuller House" season two have fallen 67% from its first season, which made the spin-off Netflix's highest-rated show.

The research company measured viewing of the show's new season opening episode from its premiere date on December 9 plus the following three days among the audience advertisers desire most, adults under the age of 50. It found a dramatic decrease from the first season premiere episode's 10.2 rating to the season two's premiere rating of 3.2.

SymphonyAM reports that only 9% of viewers who watched the first season premiere episode returned for season two's premiere.

Binging of the entire second season also saw a huge decrease for the same period from a 5.3 rating for the first season to a 2.0 - a 62% decrease.

Famous for refusing to reveal its viewership data, Netflix has called SymponyAM's ratings "remarkably inaccurate."

But "Fuller House" creator Jeff Franklin told Business Insider in an interview ahead of the second season premiere that he accepted independent ratings numbers about his show, even though Netflix never confirmed them to him personally.

"If these independent research numbers are to be believed, and there's no reason for me not to believe them, it's not only the No. 1 show on Netflix, but it's the most-watched show on television," he told us of "Fuller House's" first season.

Aside from Netflix claiming SymphonyAm's ratings aren't correct, there are a couple more caveats to this data.

First, Netflix's business model is based on subscriptions, not advertising, so the 18-to-49 ratings really just place their series in context with the broadcast networks.

And second, Netflix's originals are offered internationally and SymphonyAM only measures US viewership.

Netflix didn't immediately respond to Business Insider's request for comment on these ratings numbers.

See SymphonyAM's infographic showing the steep ratings decline for "Fuller House" below: