NEW YORK: Publishers need to understand the viewability measurement methodologies their vendor uses and establish a viewability baseline rate for use in negotiations, a leading industry figure has said.

"As a publisher, you need to understand what you can deliver, and then what you can bring to market and transact," according to Rob Rasko, founder of 614 Group, which has issued a white paper on this issue.

In Viewability: State of Operations Analysis and Vendor Study, the digital consultancy identifies two major issues it says have limited the adoption of transacting media based on viewability.

These are discrepancies in viewability counts and a lack of forecasting preparedness.

"It's time for a reset of expectations around viewability," Rasko told Ad Exchanger, as he reported that "every single vendor answered that they measure in a slightly different way and count NHT (non-human traffic) in a different way.

"If they're all counting in a different way, how would you expect the numbers would match up?" he asked.

The white paper noted that as 100% viewability is currently unattainable, "publishers and buyers will need to transact their buys based on a defensible viewability baseline rate for each publisher".

It suggested that the viewability base rate could then act as the starting point for all media-buy negotiations, including upfronts.

Separately, David Gunzerath of the Media Ratings Council, argued that while overall viewability rates hadn't improved in 2014, that might be because of the improvements that have occurred in measuring viewability in a wider range of environments.

Measured Rates, or the percentage of impressions for which the viewable status of the impression can be determined, "have undoubtedly improved significantly over the last 12-18 months", he told MediaPost.

He expected that viewability rates would improve further in 2015 and said the MRC was aiming to reduce the variation in viewabilty rates recorded by different vendors for the same campaign to "no greater than 5-10%".

"We think buyers and sellers should focus more on viewable impression counts than viewability rates as the transition from buying and selling on served ads to viewable ads progresses," he said.

Data sourced from Ad Exchanger, MediaPost, 614 Group; additional content by Warc staff