There is a growing chasm between people who watch broadcast TV and those who watch streaming shows. Consider that in 2015, Netflix subscribers watched CBS shows 42 percent less than non-subscribers. That means nearly half of Netflix subscribers have just stopped watching CBS. Netflix subscribers also watched Fox 35 percent less, ABC 32 percent less, and NBC 27 percent less.

These numbers come from a new report released by Michael Nathanson of research firm MoffettNathanson. Nathanson is tracking shifts in TV viewership over time, and he estimates that 2015 saw a 3 percent drop in TV viewing. This is part of an overall trend that saw a precipitous decline in TV viewership in 2014, combined with a corresponding rise in subscriptions to streaming services. In an attempt to keep up with these changes, most networks are now using a new Nielsen ratings metric called "live plus 7" or just "L7," which bases audience numbers on how many people watched the show—via DVR or streaming—within seven days after it aired live.

About half of last year's drop in network viewers was caused by Netflix, based on the company's claim that they streamed 29 billion hours of video in 2015. Those hours would account for about 6 percent of overall L7 viewing in the US last year, and it meant that Netflix took a solid bite out of overall viewership numbers. Nathanson predicts that Netflix will account for 14 percent of all TV viewing by 2020.

One of the only TV companies that Netflix viewers seem to love is Disney—people who subscribe to Netflix watch 11 percent more on Disney networks than people without Netflix. Age is probably a factor here, especially when you consider that CBS viewers (typically an older demographic) are dropping the most among Netflix subscribers. These numbers will no doubt encourage more networks to develop their own streaming services in order to capture viewers who might otherwise go to Netflix, Amazon, and Hulu.

While the barrage of excellent new shows on Netflix is one reason that people are defecting from traditional networks, it's also clearly a matter of convenience. A growing percentage of households only get their media via broadband, so streaming is the most obvious option for TV. Plus, Netflix offerings are designed to be consumed any time you like. No need to buy more devices to get time-shifted shows.

Of course, Netflix isn't killing the networks. It's just pushing them to adopt new streaming tech faster. It's easy to imagine a future where Netflix is no longer competing on the basis of its technology, because every network will have its own streaming service (or lucrative deals with already-existing ones). At that point, Netflix will have to compete on content alone.