  Eclipse, an open source software project, acknowledges its donors by
presenting donation badges in its issue tracking system Bugzilla. However, the
rewarding effect of this strategy is currently unknown. We applied a framework
of causal inference to investigate relative promptness of developer response to
bug reports with donation badges compared with bug reports without the badges,
and estimated that donation badges decreases developer response time by a
median time of about two hours. The appearance of donation badges is appealing
for both donors and organizers because of its practical, rewarding and yet
inexpensive effect.
