• by Gavin O'Malley  @mp_gavin, April 11, 2012

Forget about click-through rates. When it comes to online video advertising, it’s the “completes” that count, according to new research from Vindico.

“Click-through rate was created in a neophyte ad world dominated by display and search,” according to the video ad platform. “It should play a small part in measuring the success of a video campaign alongside other more powerful measures, like completion and engagement.”

Rather, advertisers should evaluate a range of variables when evaluating performance, such as whether their video ad ran as in-banner alongside content or "below the fold." These situations would likely account for high impressions with low CTR as viewers are most likely not viewing the ad when it’s playing at the bottom of a page.

Judging by "completes," mid-roll is the clear way to go, as they achieve the highest completion rates (94%) of all ad positions in 2011, Vindico found, based on tens of billions of ad impressions served in 2010 and 2011.

Video ads placed during long-form content had a higher completion rate -- 88% -- than those placed with short-form content, 76%.

In other words, a viewer who makes the commitment to watch a 30-minute episode is more invested in watching the associated ads, while a comparatively less-invested viewer “snacking” on short-form videos is somewhat more likely to click away when presented with an ad, Vindico finds. Completion rates across site types indicate that premium content on video centric sites yield higher completion rates.

Overall, 2011 was a year of massive growth in online video ads, according to Vindico -- as it saw a 134% growth in digital ad volume and 16% growth in average campaign size.

Ad-served impressions also rose last year as marketers pushed for ad-serving to be used on their digital video ad campaigns. Year-over-year, Vindico saw a 92% increase in ad-served impressions, with ad serving making up nearly half of all total impressions delivered.

That said, attention spans remain short, Vindico finds. As such, 15-second ads remain the most successful (78%) with audiences; while 60 seconds are the least (54%).

Also, despite the growing prominence of online video, marketers are still unlikely to splurge on platform-specific content. In fact, all but 2% of video ads were repurposed TV creative in 2011.

A well-strategized digital campaign always takes into account video ad frequency and its effects on viewers, Vindico notes.

Studies by the ad platform have shown that there is a frequency “sweet-spot” for marketers to keep users most interested and engaged. After frequency reaches this point, the completion rate for a campaign may drop. Ad serving helps advertisers control the number of times a user is exposed to the video ad, thus preventing “viewer fatigue.”