"Engagement is the unit of monetization"

From report What we know of digital journalism by Bill Grueskin et al.

Shanahan points to a website for a 90,000-circulation newspaper that serves a medium-sized city on the East Coast. (The name of the company is confidential because it’s a client.) This site gets around 450,000 unique visitors a month.
But those visitors differ widely, and Shanahan separates them into four types: The most loyal are the “fans,” who visit at least twice a week. Then there are the “regulars,” good for one or two visits a week. Sliding down the loyalty scale are “occasionals,” who stop by two or three times a month; and finally, the “fly-bys,” who come just once a month.
The most loyal visitors are a very small part of the overall audience: Fans make up just about 4 percent of the total number of visitors, and regulars 3 percent. Occasionals account for 17 percent and fly-bys for more than 75 percent of the total. In other words, more than three-fourths of the people who visit this news site do so just once a month.
Then Shanahan went deeper, to see how the different kinds of users behaved on the site. He knew the most loyal fans would generate more page views than the fly-bys, since fans visit the site more often. But the disparities in usage were far greater than one might expect.
Fans, despite their small numbers, were responsible for more than 55 percent of the site’s traffic. Fly-bys—those people most likely to come from a search engine or a blog—clicked on barely three pages a month. Overall, each fan generated about fifty times more traffic per person than a fly-by.
“When people talk about the size of an audience, that’s a sham,” Shanahan says. In his view, stated numbers don’t reflect how differently the varieties of users act in the way they navigate a site. Publishers mistakenly focus on “page views rather than length of time,” he writes on his blog, Digital Equilibrium. Referring to ad “impressions,” which are views (not clicks) of ads, Shanahan adds, “Using today’s standard, there is no difference between impressions that last one second, ten seconds, or two minutes.”
“The digital world has changed the revenue dynamics for publishers,” he adds in another post. “In the print world, a publisher’s shipment of physical media was the basis for generating revenue. In the digital world, consumption of media is the basis for revenue…. In other words, engagement is the unit of monetization.”
http://www.cjr.org/the_business_of_digital_journalism/chapter_two_traffic_patterns.php?page=2