Experimental Design
Our experiment simultaneously varies three factors of the subscription offer. Each factor has two levels leading to a 2x2x2 experimental design.
* Subscription Renewal after the Promo: The first factor is the subscription renewal after the end of the promotional trial, which is either auto-renewal or auto-cancellation. A reader who takes an auto-renewal promo contract becomes a regular paid subscriber after the trial period is over, by default, unless the reader explicitly terminates the subscription. On the other hand, a reader who takes an auto-cancel offer does not become a paid subscriber by default. Instead, the reader can actively choose to resume the subscription access the next time she hits the paywall, through a pop-up on the platform's home page, or by clicking on a link in any one of several emails the platform sends the reader with an aim of reinstating the subscription.\footnote{Approximately 5 days before the end of the trial offer, an email with a renewal prompt is sent to the reader, and a restart of the subscription can be initiated with a click on this email. If a reader does not respond to this email, she will be targeted in several follow-up emails as part of the standard process.} In each of these methods, the reader verifies her already entered payment information and confirms the subscription contract.
* Duration: The second factor is the duration of the experimental offer, which is either two weeks or four weeks.
* Promotional Price: The third factor is price for the promo period, which is either \euro{0.99} or \euro{0}. The price after the experimental offer is identical across individuals, and so is the set of contracts they can choose from.