LONDON: Above-the-fold is a poor proxy for viewability, while specific metrics suffer from vendor discrepancies and non-measureable inventory, according to a new study.

Quantcast, a provider of real-time advertising services, analysed some 5bn impressions per month across more than 10,000 publishers on every major RTB exchange for its report, Viewability: what smart marketers need to know.

It claimed to have evaluated every major MRC-accredited viewability vendor in multiple rounds of head-to-head testing and had concluded that in the UK the average discrepancy between vendors was just 7%, although the maximum it had found was 33%.

Further, 10% of inventory was typically not measureable at all for viewability. The report noted that this could adversely affect campaign performance for those advertisers measuring to a strict viewability goal.

"Viewability can sometimes be more hindrance than help," noted Matt White, UK managing director.

In fact, there is a very limited supply of very high viewability inventory, the report said. "Inventory with viewability above 80% constitutes just two to three percent of all RTB inventory in Europe" – and this could cost twice as much as regular inventory.

Nor should marketers think that simply placing ads above the fold is a valid proxy for viewability – depending on the exchange involved, viewability rates could be as low as 44% or as high as 65%.

The smart marketer of the report's sub-title will understand the performance trade-offs involved in having a viewability goal and decide an "optimal viewability rate" based on campaign parameters such as budget and the mix of prospecting and re-targeting and then hold all partners to the same standards.

The debate around viewability metrics is further complicated by the use of non-standard ad formats, such as skins and wallpapers, where one ad tech company reported the discrepancy between vendors ranging from 5% to 85%.

InSkin has now teamed up with MRC-accredited Moat, whose reports on campaigns run by InSkin will include viewability rates and in-view time across all types of ad format and device.

Data sourced from Quantcast; additional content by Warc staff