Collective Upkeep

We design mechanisms for maintaining public goods which require periodic non-monetary contributions. Utilitarian welfare is maximized by concentrating contributions among low-cost group members, but such policies generally induce some members to leave the group or misreport their preferences. To forestall exit, contributions must be shifted from members with intermediate costs to some high-cost members. To deter misreporting, members must be screened using up to two membership tiers, which reward larger contributions with increased access to the good. We apply our results to the design of platforms such as Netflix and TikTok hosting crowd-sourced recommendation engines, which function as public goods supported by user feedback about new content.