Online marketers are forever looking to perfect the recipe for foolproof viral videos. But those chasing that dream should take note of a new study from Harvard Business School.

After analyzing popular film and game videos online for a year, HBS marketing Professor Anita Elberse found one pretty dependable predictor of viral success: big traditional advertising buys.

Together with Visible Measures, Elberse tracked a year’s worth of popular trailers from 33 movies and video games. The professor then compared their popularity scores with things like their daily advertising budgets.

Only interested in viral videos linked to a commercial product like a film or game, Elberse found the most popular online trailers often had the biggest budgets. According to Forbes:

“In effect, the videos that got watched the most on the Internet are
those that bought their popularity through traditional offline
advertising, especially on TV.”

As Elberse put it:

“Most of the time, you have to spend money to make money online. This is not to say that viral hits can’t happen out of the
blue. They do, but they are the exception.”

Of course, there’s also the fact that the relationship between an advertising budget and a video’s
popularity online is not the same as the connection between online popularity and box office revenue.

Unfortunately, viewers who get excited about video content online aren’t always ready to go out and purchase those products.

For example, one of the films Elberse studied was the Michael Cera/Jack Black comedy “Year One.” After deploying its multimillion-dollar advertising budget, the “Year One” trailer became one of the most popular videos Elberse examined. As Forbes writes:

“The popularity of the Year One video, Elberse theorized, had
much to do with the inherent appeal of the film’s subject matter–sex!
music! dinosaurs!–to the adolescent boys who are among YouTube’s most
powerful power users.”

But that appeal didn’t translate into revenue. The movie was a stunning disappointment at the box office. (After a lackluster opening weekend, The Observer called it “easily one of the worst movies of the year.”)

As I wrote last month, the viral success of Weiden + Kennedy’s wildly popular Old Spice commercials did not translate directly into sales. In the end, it turns out that discounts and coupons contributed to a bulk of Old Spice’s sales this summer.

As Forbes points out, the “Man Yor Man Could Smell Like” ads originally became popular because of a very expensive traditional media buy: TV ads during the Olympics.

In the end, viral success may simply be a proof of success for marketing campaigns, not an indicator of future sales. For those considering investing in content that will go viral, it’s probably a good idea to think about what you’re looking for before jumping in to the space.