One of the media business’s best-kept secrets isn’t entirely confidential after all: Netflix audience ratings.

Select content companies have been turning to San Diego-based Luth Research, which has assembled a sizable panel of Netflix subscribers in the U.S. as a means of determining the most popular programs on the streaming service.

An analysis shared exclusively with Variety revealed the numbers for many of Netflix’s most recently launched original series — including which new shows already seem to be challenging “House of Cards” in popularity.

“Daredevil,” the first of multiple superhero dramas coming to Netflix as part of a deal with Marvel, premiered April 10, and is seeing strong sampling, with an estimated 10.7% of subscribers watching at least one episode in its first 11 days on the streaming service.

By way of comparison, the third season of “House of Cards,” which premiered Feb. 27, attracted 6.5% of subs over its first 30 days of availability. New comedy “Unbreakable Kimmy Schmidt” also bettered “Cards” in its first month (7.3%), while new drama “Bloodline” appears to be a slow starter (2.4%).

Still, any way you look at it, “House of Cards” is clearly a big attraction for Netflix. When all three seasons of the show are taken into account, the program has been the most popular series on all of Netflix in March (6.4%). Its third season was also binge-viewed more than any of the other aforementioned originals, with nearly half of subs having watched at least three episodes in a single day in the first 30 days after release.

The data was drawn from a sample of 2,500 Netflix subscribers watching via computers, tablets or smartphones. There’s one caveat: Luth Research does not yet track Netflix viewing on TVs, whether Internet-connected sets or those linked to streaming-media players or gaming consoles. Because Netflix hasn’t offered much recent insight into its audience composition across devices, it’s not easy to conclude whether TV viewers watch different programming than those watching via other platforms.

But the data provides a rare glimpse into viewing patterns on Netflix, which has frustrated many in its refusal to divulge audience data. That’s proved problematic for producers creating original programming for Netflix and for the studios that pocket billions of dollars in licensing fees from the company.

Netflix declined to comment regarding the Luth findings. While the streaming giant’s execs have credited the sophistication of their extensive user data with helping inform everything from their content-acquisition strategies to audience-recommendation-engine algorithms, the company has also long held firm on its disinclination to publicize any measurement findings. Because Netflix does not carry any advertising, the company professes not to care when a subscriber watches content.

Luth Research captured the viewing behavior with its ZQ Intelligence tool, which the company bills as an “industry-first” solution capable of extracting encrypted data within Netflix’s apps. Luth can drill down to viewing patterns on an episode by episode basis including audience demographics cross-indexed with user behaviors outside of Netflix.

ZQ Intelligence hasn’t been the only third-party research source to shed light on Netflix viewing patterns. Companies tracking broadband usage like Procera Networks have been able to calculate the consumption of specific programs, but Netflix has made adjustments to thwart such efforts.

With its focus on device-based Netflix consumption, Luth Research could prove a good complement for industry research giant Nielsen, which has pledged to offer measurement of subscription VOD services over connected TVs. However, that data isn’t expected to extend to Netflix original programming.

As with Nielsen data, the Luth numbers can provide an approximation of the audience size for a given series. For instance, if 10.7% of the 40.9 million domestic subs Netflix has watched at least one episode of “Daredevil,” that would mean nearly 4.4 million tuned in over the first 11 days. The 2.3% who tuned in first day of release? 940,000 viewers.

That’s far from an exact comparison to Nielsen ratings for particular episodes, but they can provide a ballpark sense of just how many are watching top shows on Netflix on a given night or over a given period.

Luth expects to add Amazon Prime–which also doesn’t disclose its audience data–to ZQ Intelligence later this year, according to Becky Wu, senior executive VP at the company. Luth began offering ZQ Intelligence in March and has data going back to the third quarter of 2013.