How effectively do you measure reach?

Back when the only magazines we could subscribe to were delivered to physical mailboxes, publishers could tell advertisers how many subscribers received each issue.

That didn’t guarantee that the story mentioning your new product was read by everyone—or anyone—but there was a tacit agreement between publishers and advertisers that circulation figures were an acceptable proxy for “reach.” Even if they didn’t really tell you whether you had reached anyone.

As publishing has moved online, that agreement has morphed into a belief that the number of clicks on a page is akin to someone getting a magazine in their mailbox. Of course, the numbers are bigger, which seems exciting—but what difference does it make to your bottom line?