Online Video Ads Don’t Threaten Traditional TV: StudyHere’s a fun fact that summarizes RBC Capital Markets’ David Bank’s conclusion from his thorough examination this morning of the video ad marketplace — and the potential threat that digital poses to broadcast and pay TV: An entire week of YouTube is roughly as valuable to major advertisers as a single, first-run episode of The Big Bang Theory. “Is The Big Bang Theory a big show? Yes,” Bank says. “Does its scale threaten the fabric of the rest of the TV advertising ecosystem? We do not think so.” That’s one reason the analyst says the market isn’t a zero-sum game, and is big enough to support growth in digital and traditional video ad sales.

It’s an important issue for investors. Many are becoming wary about conventional TV’s prospects as the ranks of people who watch video on their smartphones, tablets, and PCs grow. Last year was the first in which people spent more time with digital devices including their phones than they did with TV, and the gap between the platforms will continue to grow. No wonder advertisers also are looking seriously at digital, which companies including Google, Yahoo, and AOL encouraged at their NewFront presentations. Sales to national and local Web video providers have grown an average of 20.6% a year since 2009 vs 4.9% a year for national and local TV.

But digital has an Achilles Heel: Only about 16% of its inventory accompanies content that Bank considers “premium,” meaning that it would be suitable for a network TV advertiser. Google sites led by YouTube account for about 31% of online video minutes, but just 4% of the medium’s ad minutes. When you look closely, then, roughly half of the Internet’s premium ad inventory involves the Big Media companies themselves showing their content on sites such as Hulu, CBS.com, ABC.com, and Turner.com. When you take them out of the equation, total premium online video inventory only amounts to about 10% of the minutes that broadcast networks sell to reach 18-to-49 year olds, and less than 1% of cable networks’ inventory to reach anyone.

The bottom line: “Limitations on premium inventory, unfavorable pricing, and lower reach across broad demos keep Online Video Advertising from being a mass substitute for Network TV,” Bank says.