|Abstract:||Some user-contributed content (UCC) applications, such as Yahoo!Answers,Wikipedia,
and YouTube have drawn much media attention. Various reasons motivate the tremendous
contributions to a few UCC systems so far. Existing literature has uncovered
many factors that affect users’ decisions to become contributors [Bryant et al., 2005],
to continue contributing [Nov, 2007], and to increase contribution [Chen et al., 2007],
but none of them pay attention to why active contributors decide to stop contributing.
The exit of active contributors may affect quantity and quality of content provision on
Indeed, preliminary evidence shows that there is a reason to worry about the long
term sustainability of some systems. In 2000, Adar and Huberman’s study on the
Gnutella network showed that there was high level of free-riding on this network. Five
years later, Hughes et al.  find on the same network free-riding has gotten worse:
the percentage of users who do not share any files has increased from 66 % to 85%.
In the mean time, Andrew Lih, one active Wikipedia research/contributor also blogged
about its growth rate slowing down dramatically in late 2006 [Lih, 2007]. To what
extent is this due to contributors leaving the system? If so, who left? And for what reasons?
Answers to these questions are useful to UCC system designers for determining
the impact of contributors leaving or for devising mechanisms to prevent them from
In this study we focus on one system, Wikipedia, and analyze why some editors
stop contributing. We chose Wikipedia for a number of reasons. First, it has a large
number of active contributors. By mid-2006 over 10,000 editors had made more than
100 edits [Kittur et al., 2007]. Second, Wikipedia maintains a detailed record of its
contributors’ activities, and shares its database online.