It’s hard to imagine now, but when the US-version of The Office first premiered on NBC in 2005, the show was panned by both critics and audiences. People thought it was unoriginal, unfunny, and a bad clone of the UK version. But NBC made the call to renew the show anyway. It seemed to be the right one, because from season two onward, The Office US was winning plaudits everywhere, which lasted nine glorious seasons.

In the age of streaming, however, many TV shows aren’t afforded the same courtesy nor given the time to prove their worth. Data from media analytics firm Ampere Analysis suggests that on average, a Netflix Original gets just two seasons before being canceled.

Last month, sci-fi show Altered Carbon was inducted into Netflix’s expanding season-two cancellation club, joining Sense8, The OA, and Luke Cage in being axed after just two seasons. What followed was the now-traditional furious fan campaign to save the series from an early death.

Apart from the one-off Sense8 movie finale, which was commissioned following an aggressive campaign from fans, most attempts to bring a Netflix Original back from cancellation often fail. The company’s decision to cancel a show is often final—just ask #SaveTheOA. But while it’s sad for fans to see a show cut dramatically short, for Netflix it comes down to the data.

Netflix doesn’t release rating figures in the same way as linear television networks, but it’s been widely reported that it decides to renew or cancel its shows based on a viewership-versus-cost-of-renewal review process, which determines whether the cost of producing another season of a show is proportionate to the number of viewers that the show receives. “The biggest thing that we look at is, are we getting enough viewership to justify the cost of the series?” Netflix’s vice president of original programming Cindy Holland said in 2018, during the Television Critics Association’s summer press tour.

Shows can have a dedicated fan base, like Altered Carbon and The OA, but they might not have been successful enough to have amassed a Netflix-wide viewership. Tom Harrington, an analyst at Enders Analysis, explains that the ideal show for Netflix is one where the large majority of people who subscribe to Netflix will watch it, and not just one dedicated fan base. Something like Stranger Things can bring in new audiences, and maintain current ones, which is why it keeps getting renewed.

According to a letter sent to the House of Lords Communications and Digital Select Committee, Netflix also considers three other metrics when it decides whether to cancel or renew a show. It looks at two data points within the first seven days and first 28 days of a show being available on the service. The first is Starters, or households THAT watch just one episode of a series. The second data point is Completers, subscribers who finish an entire season.

The final metric is Watchers, which is the number of subscribers who watch a show. In an interview with Vulture, 28-day viewership, which refers to the number of people who watch an entire season of a show within a month, was consistently referenced as one of the metrics used to decide renewal. All of that data helps Netflix paint a picture about whether to renew your favorite series.

More money is on the line for Netflix as well. Like other streaming services, it differs from traditional television networks in that it commissions an entire season of a show at once, rather than just a pilot episode. Netflix also employs a cost-plus model, which means that it pays a show’s entire production costs, plus a 30 percent premium.