  We model social media as collections of users producing and consuming
content. Users value consuming content, but doing so uses up their scarce
attention, and hence they prefer content produced by more able users. Users
also value receiving attention, creating the incentive to attract an audience
by producing valuable content, but also through attention bartering -- users
agree to become each others' audience. Attention bartering can profoundly
affect the patterns of production and consumption on social media, explains key
features of social media behavior and platform decision-making, and yields
sharp predictions that are consistent with data we collect from EconTwitter.
