  Many online communities rely on postpublication moderation where
contributors, even those that are perceived as being risky, are allowed to
publish material immediately and where moderation takes place after the fact.
An alternative arrangement involves moderating content before publication. A
range of communities have argued against prepublication moderation by
suggesting that it makes contributing less enjoyable for new members and that
it will distract established community members with extra moderation work. We
present an empirical analysis of the effects of a prepublication moderation
system called FlaggedRevs that was deployed by several Wikipedia language
editions. We used panel data from 17 large Wikipedia editions to test a series
of hypotheses related to the effect of the system on activity levels and
contribution quality. We found that the system was very effective at keeping
low-quality contributions from ever becoming visible. Although there is some
evidence that the system discouraged participation among users without
accounts, our analysis suggests that the system's effects on contribution
volume and quality were moderate at most. Our findings imply that concerns
regarding the major negative effects of prepublication moderation systems on
contribution quality and project productivity may be overstated.
