The defaults were caused by a static image being served in place of rich media because the Flash-based ad format was not supported. The most recent Sizmek Mobile Index report also found a much higher interaction rate for desktop ads compared to mobile ads, again attributable to Flash mobile ads defaulting to static ads.

?Mobile inventory is growing, just like everyone expects, but campaigns are not keeping pace when it comes to compatibility with that inventory,? said Andy Kahl, director of research at Sizmek. ?This is resulting in a lot of lost opportunity and a lot of wasted impressions.

?[The most surprising finding was] the scale of the waste,? he said. ?When a rich media campaign can?t fire off its bells and whistles because its format isn?t supported, it defaults to a static image ? losing all of its interactivity capabilities. 

?This happened over 5 billion times in Q1 ? a huge amount of waste and tons of lost opportunity.?

Marketers are increasingly embracing rich media to reach potential new customers on mobile with immersive, engaging content. However, from these findings, it is clear marketers need to take a closer look at how they deliver rich media to ensure their ads are seen as intended, which could help increase the return on investment. 

Sizmek?s research shows that mobile ads tend to get more clicks than desktop. However, the interaction rate ? which is defined ad the total number of interactions out of the total number of served impressions ? is nearly five times higher for desktop ads than for mobile. 

The difference in the interaction rate is attributed primarily to Flash mobile ads defaulting to static ads, meaning a click is the sole opportunity for interaction. 

Key findings from the report include that HTML5 ads outperformed Flash ads by 400 percent in terms of interaction rate. 

Additionally, while rich media ads that relied on Flash defaulted over 98 percent of the time, those in the HTML5 format only defaulted at a rate of 8.3 percent.

Some marketers? rich media efforts are failing completely on mobile, with 12 percent of advertisers never serving a successful rich media ad to a mobile device. 

The rate of rich media failure was much lower on desktop inventory, where 60 percent of advertisers default at a rate of less than 3 percent, according to Sizmek. 

?Short-term, using targeting capabilities to target away from mobile inventory if your ads won?t be compatible [can address the problem],? Mr. Kahl said. 

?But obviously removing yourself from the mobile advertising game isn?t a sustainable strategy,? he said. ?The best solution is to switch to HTML5 for rich media campaigns ? which is compatible on mobile devices.?