The secret to Google’s success has been the ability to give advertisers access to the ROI figures of their search campaigns, quickly and effectively. Not so easy with display as anyone who works in display will tell you, no one clicks on display advertising.

That’s where Campaign Insight comes in.

AdAge explains how it works:

“With Campaign Insights, Google takes data from the advertiser’s server logs to determine who was shown an ad and when. Then compares that to web searches and site visits culled from data from the millions of Google toolbars on computer desktops. Those results are compared to a comparable group that didn’t see the ad.

Then Google measures the difference between the number of brand searches and site visits between the two groups. To filter out the impact of other media or influences, such as a TV campaign, Google compares the data to the two groups’ behavior before the campaign began. The incremental difference is attributable to the display-ad campaign.”

Google has an advantage here over other ad exchanges, Double Click, as well as the enormous amount of computers that the Google tool bar is installed on. Now we know this isn’t a perfect way to measure the success of a campaign but if Google can convince advertisers that display has had an impact on their search traffic then maybe they can convince them to spend even more via this channel.

Watch this space.