Just how big is YouTube? At an event for advertisers in New York City this evening, YouTube CEO Susan Wojcicki said that YouTube is now reaching more people in the oh-so-coveted 18-49-year-old age demographic on mobile than any TV network is period. That's a big followup from the stat YouTube announced last year, that it was beating out TV networks on reach in general — not with mobile alone. "Let me tell you from running a service," Wojcicki said, "that is not easy to achieve." That said, it's worth remembering that this is a measure of how many people YouTube is reaching, not necessarily hours watched, and YouTube has the advantage of being a global service.

Though Wojcicki didn't share hard numbers, she said that the number of people visiting YouTube is up 40 percent from last year. Wojcicki also said that time spent on YouTube is up 50 percent. These are big figures for YouTube to be hitting as it passes its 10-year anniversary. YouTube has been starting to back its breakout stars in increasingly public ways, and these stats make it sound like it has a lot to work with. The question remains how well YouTube will be able to funnel each star's success into additional series — or how it'll be able to keep pulling out stars from its network of amateur creators. Although, YouTube's network gives it plenty to choose from.

YouTube's strength on mobile is also particularly good news for Google as a whole. During its earnings release last week, Google discussed how mobile is a weak spot that it's working to address. It isn't able to charge as much for advertising on mobile as it can on the desktop, whereas YouTube is likely a much different story. The strength of mobile viewing is a point that's been popping up during this week's NewFront presentations — advertisers don't care so much what platform people are watching on, so long as the ad is tailored properly to the medium. That's an area where YouTube can help Google out in a major way, and the stats it's giving out tonight are part of its attempt to explain to advertisers why they should get on board.