Figures from Q2 2015 showed that just 49% of UK online ads could be considered ‘viewable’ based on the IAB and MRC definition of 50% of the ad being in view for at least one second. In Q2 2014, that figure was 56%. This is according to research from European ad verification company Meetrics.

This proportion is well below that of Germany ( 64%) and France ( 62%), where automated ad buying techniques such as programmatic are less common. According to a recent IAB study, 45% of UK ads were bought programmatically in 2014, compared with 28% in 2013. This is predicted to rise to 70-80% in the next three years.

When Meetrics cross-referenced its data with that of the IAB’s digital ad spend report, it estimated that around £485m was spent last year on display ads that weren’t seen.

“There’s no doubt programmatic brings many benefits to advertisers but there’s a flip side to every coin,” said Anant Joshi, Meetrics’ director of international business. “It’s certainly less transparent than buying directly and there’s also a big question mark about the quality of much of the inventory sold this way and, clearly, that most of it never ends up being seen.”