Understanding rollover data

Internet service providers (ISPs) have been facing heavy competition to attract more users in the mobile data market, along with growing operational costs. Most mobile data plans charge users a fixed fee for a monthly data quota, and any unused data at the end of each month will be wasted. In the beginning of 2015, both AT&T and T-Mobile reinstated rollover data plans with constrained eligibility. Users could then keep the unused portion of their monthly data quotas for use in a future month(s). In this work, we evaluate the benefits of rollover data for both ISPs and users as well as identify the types of users who would upgrade to rollover data plans. To do so, we consider two alternatives: a smaller data plan without rollover data, and a more expensive data plan with larger monthly quota that does include rollover data. We find that moderately price-sensitive users benefit from rollover data: price-insensitive users would not have any data to rollover, while extremely price-sensitive users would not find the rollover data worth its higher cost. Under specific bounds on the size of the rollover data plan's monthly quota, we find that users can obtain more utility and ISPs can profit from rollover data, which is verified on one year of usage data from a U.S. ISP.