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One big difference between regular TV and streaming TV is that streaming TV is pretty murky when it comes to numbers: We don’t know much about how many people are watching streaming TV services, or what they’re watching.

So here’s a little bit of light, courtesy of a new report from comScore: A chart that shows us the relative popularity — and usage — for Netflix, Hulu, Amazon Video and YouTube.

Most important caveat here: ComScore’s data, from December 2016, is measuring video streamed over Wi-Fi, at home, to TV sets. So it’s missing what’s happening on phones in and out of homes — which is a big deal — and what’s happening over wireless networks — a smaller deal.

Still, if we assume this data is at least directionally correct, it’s helpful.

We did know that Netflix is far and away the leader when it comes to streaming TV — the service says it has about 50 million subscribers. And comScore’s data syncs up with that, pegging the service’s penetration at about 40 percent of homes with Wi-Fi.

It is interesting, though, to see how far behind YouTube is when it comes to getting video to your TV. The world’s biggest video service gets to TV sets in less than 30 percent of the U.S., per comScore.

That may explain why YouTube is going to launch its own pay TV service — though YouTube has taken pains to describe YouTube TV as a “mobile first” offering.

And while Amazon and Hulu have been making a big push to build up their offerings, they’re still far behind. On the other hand, if you compare comScore’s data to earlier estimates from broadband services company Sandvine, they may be making progress. (Yet another caveat: Sandvine is measuring the amount of data those services push out; comScore is measuring how many homes they reach. So this is apples and oranges. Still, fruit.)

The other big takeaway: People who do use Netflix use it a lot — and so do people who use Hulu. Both services engage their users for more than 25 hours a month, comScore says.

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