James Dailey, product marketing manager at Atlas, a measurement service owned by Facebook, said at the recent Advertising Research Foundation’s (ARF) 2015 Audience Measurement conference that marketers who rely on cookies to understand consumers are effectively using “broken” sources of insight.

According to Warc, Dailey said: “some of the very fundamental metrics with which you manage your digital advertising are broken.

“If you use cookies to measure reach, a typical advertiser would overstate reach by 58%. You think you’ve reached 100 people … You’ve reached 100 cookies. You’ve actually reached only 42 people.” He went on to reveal that cookie data from some of Atlas’ larger clients suggested that they were reaching more people in California than actually live in California.

“At that superficial level, the data are clearly broken.”

The main cause of this overstatement is that cookies reside on separate devices and browsers but cannot connect the various services and devices. So when an individual visits a favourite website via multiple routes, cookies are unable to determine that fact.

In order to solve the issue, Dailey said, systems will need to be created to identify specific consumers wherever they are.

“The industry is at the point of a major transition, from cookies to people.”