NEW YORK: The proportion of digital publishers using audience extension has risen sharply over the past year, with many expecting it to account for up to one fifth of their advertising revenue in the coming year, a survey has found.

Audience Accelerator, part of Rocket Fuel, partnered with Digiday to survey 228 high-level digital media and marketing professionals to establish how they were meeting advertiser demand. It found that 58% of publishers were using audience extension to serve ads to readers beyond their own pages, up from 38% in 2013.

"The unique value a publisher brings to an audience extension program is their first-party data," said Jinenne Sutherland, director of Rocket Fuel's Audience Accelerator group.

"Strategically leveraging that data across owned and operated sites in conjunction, an audience extension program creates advertising programs an advertiser can't find anywhere else," she added.

Audience extension relies on cookie-technology to track user's browsing activity and detect what they might be interested in. Publishers can tag site visitors with a retargeting cookie, enabling those people to continue seeing ads from advertisers the publisher has provided access to.

Over one third (36%) of publishers surveyed anticipated that this tactic would account for between 11% and 20% of their advertising revenue during the next 12 months.

The trend is being driven by a mix of greater publisher awareness and more demanding clients.

The survey found that publishers were 23% more likely to say they are "very familiar" with audience extension than they were last year.

And there had been a 55% uplift in the numbers including audience extension on client proposals when advertisers were demanding more reach than the publisher could deliver through its own site.

The need to go down this route becomes clear as publishers recounted how half of media buyers and brands said they would spend more with those offering audience extension tools.

There were a couple of areas which publishers felt could be improved on, however, notably reporting and transparency.

Data sourced from Digiday; additional content by Warc staff