Demand for real-time bidding inventory overtook supply for the first time during 2012, causing CPM rates to double, according to Adform’s European RTB trend report. RTB-traded mobile inventory now has higher CPMs than its desktop counterpart.

Ads on tablets were found to have a 65 per cent higher click-through-rate than on desktop, while clicks on smartphones were 50 per cent higher. Not surprisingly, display ads above the fold receive double the number of clicks as those that require people to scroll.

The total RTB market is predicted to be worth $20bn by 2015, but the report says that just 2.1 per cent of this ad budget is currently spent on smart devices.

“The RTB industry is booming but European advertisers are still testing the waters,” said Gustav Mellentin, CEO of Adform. “The fact that CPM rates have doubled over the past year shows that RTB-traded inventory is a ‘win win win’ for publishers, advertisers and consumers. Publishers can increase the value of RTB-traded inventory, advertisers will see more premium RTB-traded inventory becoming available and consumers will be served ads that are increasingly more relevant to their interests.”