One of TV's greatest secrets has been revealed: We now know how many people watched an episode of one of Netflix's shows. The Season 4 premiere of Orange Is the New Black drew 6.7 million viewers in its first 72 hours online, according to viewership data from Nielsen, The Wall Street Journal reports. Nielsen's data also showed that viewership for the second episode decreased to 5.9 million viewers.

The data, which covers the time period from June 17 to June 19, is somewhat surprising because previous estimates of Netflix viewership done by other entities have been refuted by the streaming service, which has long kept its tallies secret. These new numbers are considered reputable though, not only because of Nielsen's credibility but also because the data giant's findings were backed by Lionsgate, the studio that produces Orange Is the New Black.

To measure ratings, Nielsen used the audio fingerprinting technology available in its base of 40,000 U.S. homes. That technology recognizes audio files that studios provide of their programs.

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Major networks have frequently questioned Netflix's actual viewership — wondering aloud if the service is as much of a challenger to traditional TV as analysts (and the public) have asserted. As Variety reports, Orange Is the New Black's premiere would have been the second-most watched cable show the week it debuted. Game of Thrones' June 19 episode netted 10.4 million total viewers, and the June 13 premiere of TNT's Major Crimes came in second place with 5.8 million viewers.

The research is part of a larger partnership between Nielsen and TV studios that choose to opt-in to track viewership across streaming platforms such as Netflix, Amazon and Hulu. It should be noted that while Nielsen's numbers lend credence to the idea Netflix shows don't rank much higher than most cable fare, this data point is only important to U.S. viewership. Netflix also released Orange Is the New Black globally on the same day.