It has become customary for Google to make comparisons between YouTube and TV on its earnings calls — after all, it is hoping that brands will switch out some of their huge TV advertising budgets for online video.

Thursday's second-quarter earnings call was no exception. Google's executives made several references to how YouTube was coming after TV in a big way.

Omid Kordestani, Google's chief business officer, kicked things off with this standout stat: "YouTube reaches more 18- to 49-year-olds in the US than any US cable network."

Not only is YouTube apparently dominating in terms of reach, but people are treating YouTube like their television set.

Kordestani said: "The number of users coming to YouTube, who start at the YouTube homepage similar to the way they might turn on their TV, is up over three times year-over-year. Plus, once users are in YouTube, they are spending more time per session watching videos. On mobile, the average viewing session is now more than 40 minutes, up more than 50% year-over-year."

Those findings are extremely significant at this point in YouTube's life stage. Google wants to emphasize that YouTube is no longer just that repository of videos where people need to know what they want to watch before they want to watch it — YouTube is now becoming a discovery platform, acting as a curator of content. YouTube is mimicking the programming guide on your TV set.

And as users shift their viewing habits to online video, the advertising money is following.

Every year Google apes the TV industry's annual upfronts with its own "BrandCast" event. It's a flashy affair in which YouTube hauls out its biggest stars onstage and shows off its newest advertising products in a bid to secure big upfront advertising commitments from marketers.

"Compared to the same period after BrandCast last year ... commitments in the US were three times higher," Kordestani said. The number of advertisers running video ads on YouTube is up 40% year-on-year, and average spend per advertiser among its top 100 customers is up 60% year-on-year, he continued.

Meanwhile, the performance of the TV upfront season this year is "modestly worse than expected," Jefferies & Co. analyst John Janedis told The Wall Street Journal's CMO Today earlier this month.

Ruth Porat, Google's chief financial officer, made it fairly clear YouTube is coming after TV. She said twice on the earnings call: "Our focus is the opportunity to get the larger budgets to move to YouTube."

While Google has, for some time, been vocal about how it feels YouTube is edging up on TV, it still has a long way to go before it comes anywhere close to replacing traditional viewing.

People in the US watch TV in the traditional, "linear," scheduled way for almost five hours every day, according to Nielsen. Meanwhile, they use the internet on a computer and smartphones for roughly half that time each day.

And TV is still advertisers' biggest outlay. Global TV advertising spend reached $230 billion last year, according to estimates by the media agency Carat. Yet online video advertising spend in 2014 was just $11 billion, according to ZenithOptimedia. It's growing quickly — expected to experience a compound annual growth rate of 29% between 2014 and  2017 — but even then, at $23 billion, video ad spend will just be a tenth of what TV ad spend is today.

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