If you combine everything that you do on every website besides Netflix and YouTube — reading this article, or looking at GIFs, or checking your email — all of that combined generates about the same amount of peak web traffic as those two sites alone. Netflix itself is bigger in every metric than HBO.
According to (estimated) data compiled by Sandvine, a manufacturer of broadband technology, the video-streaming sites comprise 32.3 and 17.1 percent of all peak-period download traffic in North America, as reported by Variety. Combined, that's 49.4 percent. And at the rate that each is growing — 35 percent year-over-year for Netflix and about 24 percent for YouTube — it's a safe bet that the two will soon account for more than half of all the bandwidth we use.
Part of that is because video is bandwidth intensive, of course. Streaming video pushes a lot of data in a short time period, particularly at higher definitions. But a large part of it is because use of streaming sites is also increasing. From Variety:
Netflix said it streamed more than 4 billion hours of video globally in the first quarter of 2013, compared with 1 billion per month last June. The company has packed on customers, adding about 2 million U.S. streaming subs to stand at 29.17 million domestically — making it bigger than HBO in that regard.
Netflix has about 1 million more subscribers than HBO. But it almost certainly is also watched more, as it doubles down on binge-watching while HBO steps back from a streaming future beyond its cable subscribers.
During the beginning part of May, the highest-rated shows on HBO were Game of Thrones, Real Time with Bill Maher, and Manhunt, according to TheFutonCritic.com. Game of Thrones had the best ratings, with 2.9 million viewers in one episode and 2.4 million in another. (And that's just legally.) Maher pulled in 1.3 at his highest. Those four billion hours Netflix shared, however, comes out to about 1.8 million viewers per hour — meaning that HBO would have needed to show things with better-than-Maher ratings every hour of every day for three months in order to beat Netflix. It clearly didn't do so.
The growth of Netflix and YouTube (which does seven times better on mobile) is paired with growth in consumer broadband use. During the first three months of the year, American broadband owners used 44.7 gigabytes of data, up 39 percent. For the sake of comparison, if an internet user ten years ago had wanted to download that much data, it would not have happened in real-time. It would have taken 10.5 weeks.