The share who clicked.

The attention tax

Every channel starts with the same event: something was shown, and someone either clicked or scrolled past. CTR is the honest count of that moment, which is why the same three letters appear in ad dashboards, email reports and Search Console alike. It matters beyond the visits it counts, because platforms read it as a relevance signal. Ad auctions estimate how likely your ad is to be clicked and price you accordingly — a high expected CTR wins cheaper impressions (see CPM) and a lower cost per click, while a low one is taxed twice: fewer visitors, and more expensive ones. The figure above makes the arithmetic plain — the impressions never change, yet the price of each click falls as more people take the offer.

Same metric, three worlds

The number means something different depending on where you read it. In paid ads, CTR is mostly creative quality: the image and the first line do the work, and around one percent is workmanlike while two or three says the creative deserves more budget. In email, CTR is list health: it decays when you keep mailing people who stopped wanting to hear from you, so a sliding CTR usually calls for pruning the list, not redesigning the button. In search, CTR is position and title: the top result takes an outsized share of the clicks, so climbing a spot (see SEO) and writing a title worth clicking often beat anything you change on the page itself.