  Citizen Science is research undertaken by professional scientists and members
of the public collaboratively. Despite numerous benefits of citizen science for
both the advancement of science and the community of the citizen scientists,
there is still no comprehensive knowledge of patterns of contributions, and the
demography of contributors to citizen science projects. In this paper we
provide a first overview of spatiotemporal and gender distribution of citizen
science workforce by analyzing 54 million classifications contributed by more
than 340 thousand citizen science volunteers from 198 countries to one of the
largest citizen science platforms, Zooniverse. First we report on the uneven
geographical distribution of the citizen scientist and model the variations
among countries based on the socio-economic conditions as well as the level of
research investment in each country. Analyzing the temporal features of
contributions, we report on high "burstiness" of participation instances as
well as the leisurely nature of participation suggested by the time of the day
that the citizen scientists were the most active. Finally, we discuss the
gender imbalance among citizen scientists (about 30% female) and compare it
with other collaborative projects as well as the gender distribution in more
formal scientific activities. Citizen science projects need further attention
from outside of the academic community, and our findings can help attract the
attention of public and private stakeholders, as well as to inform the design
of the platforms and science policy making processes.
