From the beginning, online advertising has been touted as something altogether different from print, broadcast and outdoor—an advertising medium where you can truly measure results. Unfortunately, the reality is that when there is so much information to be had, it’s hard to know what’s worth focusing on. In fact, the full-on pursuit of ROI can distract not only from significant results but also from pursuing the kind of thinking we need to create truly innovative and effective marketing campaigns.

Most advertisers concentrate on click-through rate (CTR) as the definitive measure of any digital campaign. But several recent studies from comScore suggest that CTR is not the single most important measurement. By studying search, site traffic and consumer spending patterns, comScore has found a significant correlation between ad impact and consumer behavior for up to four weeks following ad exposure.

You can see from this graph that online ads have a powerful “display” function that resonates beyond the campaign itself, and is not measurable by CTR alone. As Forbes reported on a 2008 study, “comScore found readers were 46% more likely to visit an advertiser’s site within four weeks of seeing its ad online than they were if they did not view an ad.” Verso Digital’s own experience with campaigns for book publishers supports these findings.

Our own projects—on the Reader Channels and throughout the digital sphere—indicate that the most relevant campaign metric is often not CTR, but numbers that reveal other user behavior such as site visitation, engagement, and, most important, sales. While generating outstanding site-engagement, some of our most successful campaigns in fact showed only average to below-average CTRs. In one case, a pre-sales ad campaign for Thomas L. Friedman’s Hot, Flat and Crowded promoted free audio downloads. It led to over 99,000 downloads, 13,000 registered email addresses and 160,000+ users available for retargeting. In another case, an ad campaign promoting a key chain giveaway for John Grogan’s Bad Dogs Have More Fun led to over 100,000 people registering to learn more about the book. The publisher saw major traffic continuing for at least four weeks following the conclusion of the Verso Reader Channel ad campaign—with no additional publicity, promotion or advertising to support it.

CTR remains a useful metric, but only when considered in relationship to sales, traffic, search, and total impressions delivered. Campaigns on premium sites with a great book audience, such as the NYTimes.com, often generate CTRs well-above average. But because ads on the site are so expensive, the total number of people reached, and thus the total number of people who click through, is relatively small. For example, a $10,000 spend on a site with a $40 CPM results in 250,000 impressions delivered. When the CPM drops to $5, however, that same $10,000 delivers 2 million impressions. At a standard .1% CTR, $10,000 spent with a $40 CPM delivers 250 clicks. With a relatively below-average .05% CTR, $10,000 spent with a $5 CPM delivers 1,000 clicks. In this scenario, the campaign with the lower CTR actually performed better by delivering more users to the site. For this reason, CTR should always be considered hand-in-hand with total impressions delivered.

The goal of each new marketing campaign—and the measure of its success—must reflect the resources at hand and how you can best reach the community of potential readers. What doesn’t change is the need for flexible ideas and an ability to think through each niche effort in its full context.