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Click-through rate (CTR) is often used to describe the advertising performance on a publisher’s site. CTR for an ad is defined as the number of clicks on an ad divided by the number of times the ad is shown (impressions), expressed as a percentage. If the ad sales team for a publisher claims 1 million monthly unique visitors with 4 million page views and a CTR of 0.2% (or 8,000 click-throughs), the buyer might think those click-throughs are all distributed across the million unique users to yield 8,000 unique conversions. The buyer and the seller are wrong. Here’s the problem: CTR doesn’t take into account audience engagement, not to mention the fact that other advertisers are competing for the click-through […]