A recent chart compiled by Vox’s sister site Recode, using data from the analytics firm Jumpshot, underlines the major issues facing Netflix in the next five years.

The chart, by Rani Molla, visualizes data that Jumpshot collected from 100 million anonymized web devices. Every time one of those devices used a web browser from within the US to visit a Netflix page and play a show or movie, it counted as a view for the survey’s purposes. The survey was conducted between January and November in 2018.

Netflix is famously secretive about its viewership data (except when it purports not to be), and the absence from this chart of the network’s hit series Stranger Things, which routinely pops up in data sets like this as one of its most watched shows, does give me some pause about the accuracy of Jumpshot’s numbers.

But overall, this data tracks with information from many other surveys and offhand comments — namely, that most viewership on Netflix gravitates toward audience favorites that first aired on other networks, which Netflix itself doesn’t own. These surveys have also frequently concluded that the two most popular shows on Netflix are The Office and Friends, in some order.

But Netflix doesn’t ultimately control the streaming rights to those shows beyond the windows it has licensed them from NBCUniversal (which owns The Office and is an investor in Vox Media) and Warner Media (Friends). In the chart above, red bars denote the shows whose streaming rights are controlled by studios that have their own streaming services in the works, and thus might pull them from Netflix at any time.

As you can see, only seven of the 20 shows listed are not controlled by those other studios (though Fox technically owns Arrested Development — it’s just that its most recent seasons are Netflix productions), and Netflix’s six most popular shows are not among that number.

This chart is actually even worse for Netflix than it already looks

Here’s a crash course in what it means to “own” a show: TV networks almost never make the shows that they air. (Indeed, until the early ’90s, they were legally forbidden from doing so.) Instead, the shows are made by production companies, from which the networks license the broadcast rights for a specific window of time or number of showings.

Sometimes, production companies are very, very big — like Warner Bros. Television. Sometimes, they’re very, very small — like Tornante, a company headed by former Disney chief Michael Eisner, which makes BoJack Horseman, among others. But they are the companies actually doing the work of making sure TV shows get made. They hire talent, set budgets, and try to keep the trains running on time.

Networks are only able to collect the money they make directly from selling ads, from charging cable company “carriage fees” (which your cable company pays per consumer to the network itself), or from subscription fees (this is where networks like Netflix come in).

Production companies collect all of the other streams of revenue, like DVD sales and selling reruns of the show in syndication. Thus, airing a show like The Office was great for NBC, as any network can make lots of ad money from a hit show, but there’s substantially more money involved for NBCUniversal, which produced The Office and will make money off of it in perpetuity. (Just think about how long reruns of The Twilight Zone and I Love Lucy have run to get a sense of the money involved.)

Now, a traditional TV network has a little hack to this system, in that it is usually part of a gigantic corporation that owns a production company. In the case of The Office, for instance, the show aired on NBC, and was produced by NBCUniversal. So all of the money it made — from ad revenue to DVD sales to streaming sales to so many other revenue streams — went back to the same place.

Netflix, until very recently, didn’t have as robust of an integrated production system as other companies, so it relied on leasing content from other production companies’ libraries (shows like The Office and Friends and The Flash, which first aired elsewhere) and on purchasing its original series from other production companies. Only in the last couple of years has it finally started owning the movies and TV shows it produces outright.

But what this means is that the chart above is even more devastating for Netflix than it might look at first. By my count, Netflix fully controls the rights to only two shows on that list: Black Mirror and Big Mouth, both of which it produces in league with smaller production companies who don’t have the leverage to demand some sort of rights-sharing agreement. Every other show on the list is controlled by some major outside entity in some way or another.

Now it’s distinctly unlikely when it comes time for Netflix to reup its commitment to BoJack Horseman or Orange Is the New Black (which is owned by Lionsgate Television) that either show is going to suddenly decamp for Hulu or Amazon. There is substantial value to having your TV show on the world’s largest streaming platform. But the fact that either show could is something Netflix still has to guard against.

Similarly, a show like Frasier (whose rights are controlled by CBS’s TV library) has been consciously licensed out to all major streaming companies. That specific strategy means the show will likely remain on Netflix for some time to come.

But there are no guarantees. And as more and more media companies increasingly view Netflix not as a way to make money off their older shows while getting those shows seen, but as a competitor, the value of those shows only goes up — as a recent $100 million deal to keep Friends on Netflix for a single year suggests. And once new streaming services from Disney (which will soon control all of the assets of 20th Century Fox) and Warner Media launch later in 2019, using popular programs like Grey’s Anatomy (Disney-owned) and Friends as a lure to attract new subscribers will only become more tempting.

This is both why Netflix keeps producing its own shows and movies so frantically, and why you shouldn’t count on many of your favorites always being available on the platform. Netflix is hoping its gigantic lead in the streaming space, its best-in-the-industry interface, and its brand-name recognition will help it weather the inevitable loss of some of these popular older shows. Other media companies are hoping that a future version of Netflix that only boasts Netflix original programming will be a lot less enticing than one that offers reruns of your favorite comfort food sitcoms alongside that original programming.

I don’t know how this situation will shake out, but we’re going to start finding out very soon. Either it ends with Netflix as one of the biggest fish in a pool it has made much, much smaller just by existing, or it ends with Netflix going the way of Napster or MoviePass — a good idea that shook up the entertainment industry but ultimately boasted an unsustainable business model. Increasingly, it seems as though there’s no in-between.