As a site owner, can you justify charging 150% for placing an advert at position A compared to position B? What fraction of users see each?
Advert impressions occur far more often than clicks. But impressions don’t provide any feedback: The user has no control over whether the advert is delivered. However, they do control whether they look at it. Branding is about delivering the message, not converting sales on the spot. How can you measure the impact of marketing materials?
Compared to impressions and clicks, eye tracking provides a more complete picture. It also provides empirical evidence for passive events, such as proving the value of advertising slots allowing site owners to charge a premium for the best.