The Economist is tightening up its paywall:

At the end of January, the subscription publisher changed its metered access after six months of testing. Reader research found that on average people either read five articles before subscribing or they sign up right away. And a high content threshold would allow potential subscribers to slip through the net and never hit the paywall.

Analytics are critical to monitoring and developing a good paywall strategy, and setting the number of free article too high is a very common mistake. As the talk from Rouven Leuener of Neue Z├╝rcher Zeitung at news:rewired illustrated, you need to keep monitoring, iterating and developing your strategy.