Most publishers are too generous and need to stop more readers [with a paywall] to force conversion. 

In news just yesterday, Bloomberg and Vanity Fair were both reported to be moving to paywalls. Vanity Fair will offer three free articles a month, then readers will be required to subscribe for $19.99 a year for either digital-only or print plus digital, Digiday reported. They'll add a searchable archive of its articles, a subscriber-only newsletter and possibly even access to its writers and editors—the latter being the trend of the year, it seems like. (Read my recent article on that.)

“People need to experience the content they’re asked to purchase.”