Comparing the stats for Toprural delivered by Google Analytics with his own 3rd-party solution, he finds that, while his own system (AT Internet’s XiTi) says 37.8% of visitors come via Google, GA says it’s 71.8%. The core of the problem, he discovers, is the good old cookie window. It turns out the default cookie window Google ascribes to visitors that arrive on a site via Google is six months. Six months!

So, every visit a user happens to make to a site for the six months after having once visited that site via Google is ascribed to the search engine. The standard window for display media is 30 days, a sixth of the length Google has opted for, while we’re typically asked to assign search cookie windows of a couple of days at most.

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