When Netflix (NFLX -0.79%) announced that 45 million accounts watched its smash hit movie Bird Box, it faced a certain amount of skepticism from the usual suspects. Some wondered how meaningful the stat was, since it couldn't be independently verified. Others pointed out that it was unclear what Netflix meant when it said "watched."

The company later clarified that those 45 million customer accounts it tallied were only counted if at least 70% of the total running time -- including credits -- was surpassed. Netflix also said that even if Bird Box had been watched multiple times, it counted only one instance per account. That meant each account had completed at least 87 minutes of the two hour and four minute-long film.

Still the doubters remained. Now the company is getting support for its claims from an unexpected source -- and one that has been at odds with Netflix in the past.

A woman and two children in a rowboat, wearing blindfolds and heading into fog.

Bird Box continues to generate conversation. Image source: Netflix.

Survey says...

Market research company Nielsen (NLSN) is adding its support to Netflix's claims. The ratings service released estimates that 26 million U.S. subscribers tuned in to Bird Box during the same seven-day period Netflix cited when it tweeted about the record-breaking debut: 

Nielsen shared a few other tidbits. The program drew 4 million viewers, on average, in each of its first 10 days. In addition, viewership of Bird Box actually rose on its eighth day of release, which Nielsen said was "a very atypical event and likely attributable to the extraordinary buzz around the movie." The show also appealed to a broad swath of the population, with 36% of the audience between 18 and 34 years old, 57% female, and nearly half Hispanic or African-American viewers.

This isn't an apples-to-apples comparison for a number of reasons. Nielsen only measures programs watched on television but fails to capture viewers on mobile devices, such as smartphones and tablets. In addition, while Nielsen's ratings capture U.S. viewing, it misses out entirely on Netflix's growing international subscriber base. With 137 million total worldwide subscribers, nearly 79 million -- or 58% -- are located in international locations. 

That said, if 26 million U.S. subscribers watched Bird Box on TV during its first seven days, it's easy to conclude that the remainder came from mobile devices and international subscribers -- which outnumber their U.S. counterparts.

A history of conflicting views

It's important to note that, in most instances, the streaming giant refuses to divulge its viewer numbers, unless of course the company has something to gain by doing so. Add to that the differences in reporting methodologies, and it's easy to see why Netflix and Nielsen have been at odds in the past.

In late 2017, the ratings company reported that 15.8 million households had viewed the first episode of the second season of the Netflix original series Stranger Things during the first three days following its release. Netflix fired back, "Their math might be from the upside down," referring to Stranger Things' alternate dimension. "Nielsen only measures a fraction of our members' viewing. For example, they don't measure mobile viewing." 

That wasn't the first time the two had tangled.

In October 2017, Nielsen launched a content ratings service for a subscription video-on-demand platform, claiming to be able to estimate streaming viewers. In conjunction with its debut, it released statistics related to several of Netflix's original programs -- Marvel's The Defenders, House of Cards, and Fuller House. Nielsen said The Defenders averaged 6.1 million viewers in the first seven days following its release, while Fuller House and House of Cards captured 4.6 million viewers each. 

In response to Nielsen's claims, a Netflix spokesperson replied, "The data that Nielsen is reporting is not accurate, not even close, and does not reflect the viewing of these shows on Netflix." Again, the numbers reported by Nielsen probably missed counting both international and mobile viewers.

Only part of the story

There's little argument that Bird Box has captured viewers imaginations and entered the cultural zeitgeist, as evidenced by the buzz on social media. The movie even inspired viewers to blindfold themselves and attempt a variety of everyday tasks, a theme taken from the film. That trend prompted Netflix to issue a warning not to "end up in the hospital."

Every time Bird Box grabs another headline, it helps to boost Netflix's fortunes. As noted showman P.T. Barnum said, "There's no such thing as bad publicity."

Check out the latest Nielsen Holdings and Netflix earnings call transcripts.