As usual, Netflix isn't saying a word about how many of its subscribers watched its riveting documentary series Making a Murderer. But according to Symphony Advanced Media, which began sharing metrics for Netflix and other streaming services last month, the show has been a huge hit. In the 35 days after its release, each episode of Making a Murderer averaged 19.3 million viewers.

(UPDATE: Since this article was originally published, Symphony has corrected its numbers to reflect that Making a Murderer was actually watched by 19.3 million viewers, not 8.14 million as originally reported. The story has been updated with the corrected Symphony data, which includes increases in the numbers for Marvel's Jessica Jones, The Man in the High Castle and Transparent.)

Most of Netflix's original series tend to command the most attention in their first two weeks, according to Symphony. But Making a Murderer was an anomaly, given that it was released on Dec. 18 with none of the advanced fanfare that typically accompanies Netflix's biggest shows like Orange Is the New Black and House of Cards. But the buzz around the show, and questions about Steven Avery's trial and its outcome, steadily grew over the following week and into the holidays and early January as viewers began devouring the show.

While streaming services like Netflix and Amazon have refused to share any kind of ratings metrics, Symphony Advanced Media has been compiling data via its multiplatform measurement tool, VideoPulse.

According to Symphony's data, an average of 565,000 adults ages 18 and up watched each episode of Making a Murderer in live-plus-same-day numbers. Live-plus-seven numbers jumped to 2.3 million. Live-plus-14 was 5. 5 million. But the numbers surged over the next three weeks, as Making a Murderer's live-plus-35-day numbers jumped to more than 19 million.

That 19.3 million number is particularly impressive given that it more than doubles the live-plus-35 average rating of all broadcast prime-time shows that aired original episodes between Sept. 21 and Jan. 24: 8.5 million.

Making a Murderer's ratings are also more than double the 8.8 million live-plus-35 rating for adults who watched episodes of Marvel's Jessica Jones, which Netflix released in November. Amazon's Man in the High Castle, which also debuted in November, was viewed by 3.4 million adults in live-plus-35 numbers, while Transparent's second season, which launched in early December, was watched by 2.1 million in live-plus-35.

Last month, Symphony shared data with Adweek indicating that broadcast TV is still outpacing streaming's top shows. But today's new metrics indicate that Netflix's biggest series—like Making a Murderer and Marvel's Jessica Jones—can more than hold their own with broadcast shows.

Symphony's new data also shows that audiences gravitated to streaming originals during the December holiday period. The share of viewing duration between streaming originals and broadcast prime-time episodic programs (which exclude news, sports and specials) shows a streaming spike, which was driven by Making a Murderer, during the weeks of Dec. 21 and Dec. 28.

However, as broadcast programming returned with original episodes in the first week of January, viewers moved away from streaming and returned to their preholiday viewing patterns.

Netflix had no comment on Symphony's Making a Murderer data, but last month, chief content officer Ted Sarandos dismissed Symphony's metrics as "remarkably inaccurate," adding that "the methodology and the measurement and the data itself doesn't reflect any sense of reality of anything that we keep track of." At the time, Laura Bernstein, Symphony's svp of client solutions, brushed off Sarandos' remarks, telling Adweek, "We have confidence in our data."

Symphony uses automatic content recognition, or ACR, software embedded on a mobile app to recognize and match a program's audio files as well as URLs, for streamed content. The company also sends a targeted survey to its panelists twice a week asking which platforms they watched specific programs on to determine whether a show like Empire was viewed via Hulu, VOD, Fox Now or DVR. The company hopes to increase its panel from 15,000 to between 20,000 and 25,000 by the end of 2016.

Netflix could be in for more Making a Murderer spikes down the line, as the show's creators are already prepping a potential follow-up, even though Netflix hasn't officially ordered one.

Another takeaway from Symphony's data is that streaming services should consider targeting audiences during the holidays, when few original episodes of broadcast or cable series are airing and viewers have more time to engage with shows. That was what led Netflix to pick that time frame for Making a Murderer, Lisa Nishimura, Netflix's vp of original documentary programming, told Adweek last month.

"As we were producing the episodes, it became very clear that they demand your attention—they're very dense," Nishimura said. "It's not something you put on and then cook your dinner and watch out of the side of your eye. You really need to engage. And as you watch it, it really inspires in one a desire to talk about it, to commune with other people about it, to bounce theories and ideas and just try to process. And we know that the holiday season is one that allows more freedom of time."