The data suggests cookies tend to overestimate reach, and underestimate frequency and conversions because of the way they technically operate.
More marketers today now build their media-buying plan around reach, but with a cookie-based approach, marketers underestimate reach.
Victor Wong, CEO at Thunder Experience Cloud, which helps marketers reach consumers through data targeting, said marketers actually gain half the reach. “If a marketer tries to reach 20 million people, we estimate the reach turns out to be around 10 million.”
The data revealed that a cookie-based approach tends to overestimate unique reach by 101%, underestimate the actual frequency by 50%, and find 18% fewer ad-attributed conversions.
Historically, most ad servers like Google DoubleClick and Sizmek measured (or still do) cookies, where they count how many they see. The problem is that people delete cookies from the browser and use multiple devices.
The study also found when applying an identity graph, or a unique identifier, to the data set it will match multiple cookies from multiple devices to one person because the log-in links to the same ID.
When marketers stay with the cookie-based approach, rather than move to a people-based one, they are missing the opportunity to reach more consumers.
The inability to associate all the correct sales to having seen an ad remains the problem. For example, if a consumer viewed an ad on a desktop and purchased it on mobile, the advertiser will not know that it’s the same person. It happens to me all the time. I may view something on a retailer’s website via my laptop and then later go back and purchase the item on a mobile device. If I’m logged in the retailer knows it’s me, but if I’m not I keep seeing the same ad for what seems like eternity.
People-based measurement counts ad exposure and conversions using a person ID that combines multiple cookies and device IDs rather than using a single cookie or device ID, explains Wong. He said this doesn't solve the problem of tracking in Apple Safari -- where the advertising identifier (IDFA) is used for each iOS device that mobile ad networks typically use to serve targeted ads -- but it does help.
An identity graph would allow marketers to attribute that conversion to an ad and measure the true performance of a campaign.
The study also found a 5% difference in unique reach measured for every 100 million impressions. The data also found bigger discrepancies occurring the longer the campaign runs.