  Badges are endemic to online interaction sites, from Question and Answer
(Q&A) websites to ride sharing, as systems for rewarding participants for their
contributions. This paper studies how badge design affects people's
contributions and behavior over time. Past work has shown that badges "steer"
people's behavior toward substantially increasing the amount of contributions
before obtaining the badge, and immediately decreasing their contributions
thereafter, returning to their baseline contribution levels. In contrast, we
find that the steering effect depends on the type of user, as modeled by the
rate and intensity of the user's contributions. We use these measures to
distinguish between different groups of user activity, including users who are
not affected by the badge system despite being significant contributors to the
site. We provide a predictive model of how users change their activity group
over the course of their lifetime in the system. We demonstrate our approach
empirically in three different Q\&A sites on Stack Exchange with hundreds of
thousands of users, for two types of activities (editing and voting on posts).
