There are quite a few companies sitting on treasure troves of offline data that can be merged with online visitation data. Most media buyers think there's a lot of value in using this information for targeting purposes, and they're right. But in my opinion, there's more value wrapped up in measurement of display campaigns than there is in targeting.

But first, let's talk about the problem: Our metrics are broken.

Direct response advertisers tend to look at measures of immediate interest in order to gauge the success of digital campaigns. They look at click-through rate (CTR), the raw number of leads or sales attributable to ad clicks, and cost-per-lead/sale. The branding effect of display ads on sales is usually completely ignored. We know that's an unrealistic picture of success, but we accept it because there isn't much we can give to advertisers in order to take its place. Yet, we all know that if direct response advertisers can get a more complete picture of what their ads are doing to drive sales, they'd be doing a lot less CPC and CPA advertising and a whole lot more CPM display advertising.

On the brand advertising side, we're not doing such a great job at providing exposure metrics (see previous page), and the most widely used method of gauging branding success involves survey methodology executed by the likes of Dynamic Logic, Insight Express and Factor TG. Factor TG CEO Scott McKinley sees three legitimate issues undermining the credibility of online research studies. In addition to the conflicts of interest inherent in publisher-funded research, McKinley sees a flaw with the normative databases used to paint a picture of comparative performance.

"Everyone loves norms because they provide context for performance," he said. "'Did I do better than the next guy?' is the prevailing question. This is shortsighted. It doesn't matter how much better you did if everyone sucked. But the real problem with commonly used norms is that nobody seems to suck, which is, of course, statistically impossible. So, once again, nobody really believes what's being reported."

Additionally, McKinley thinks survey credibility is being eroded by "degraded methodology."

"Imagine the lift you would get if you compared the attitudes of a run-of-site control sample against a highly targeted, in-market audience," he said.

Our metrics are broken. We can do better than brand studies and CTR. Enter purchase data. If we can marry online and offline purchase data to a significant number of non-personally identifiable user cookies, we have the basis for a measurement system that blows away everything that came before it. Measure a pool of control users who haven't seen your ad and compare them to a group of people who were exposed to it. Look at what they purchased over a certain pre-determined period of time and compare the lift in sales.

This enables an advertiser to build dollar-in, dollar-out models for digital display. They can accurately gauge what they get back in increased sales from a given investment in digital.

Yahoo has had a model to do this in the CPG category for several years. They call it Consumer Direct, and the offline sales data come from the Nielsen Homescan panel, matched to Yahoo's vast registered user base. But we need a solution that can scale web-wide and not be limited to any one site or portal.

For agencies and publishers, adoption of a purchase data-based measurement solution means that digital will be treated more fairly when it comes to valuing its impact. For instance, a direct response advertiser that sells televisions online will understand that exposure to its ads resulted in a sales lift of X percent over a period of 60 days. The CTR-based metrics it currently uses are wildly inaccurate because it's highly unlikely that many people are purchasing televisions online as an impulse buy after a banner click.

Purchase data-based solutions present a more complete view of the success or failure of a campaign. If we could measure all our digital display campaigns this way, digital would capitalize on the increased emphasis on accountability in marketing programs.