The emergence of increasingly quantifiable forms of interactive digital advertising has resulted in advertising becoming much more of a quantitative practice. While the so-called “perfectly quantifiable” click emerged as a readily used key performance indicator for digital-advertising effectiveness, a new movement has been brewing. Its adherents favor tracking every dollar and every resulting action down to the pixel, only to then optimize, analyze, and further optimize that information to squeeze every last bit of advertising return on investment from the dollars allocated to a campaign.

In search-engine marketing, where clicks mean a great deal to the ultimate effectiveness of digital advertisements, this makes sense. In the display-advertising ecosystem, however, the tendency to optimize toward clicks makes little sense, given that clicks have been shown to bear little correlation to performance metrics such as conversion. Because “not everything that can be counted counts, and not everything that counts can be counted,” optimization can be a driving force behind both good and bad marketing performance. 1