  The 2016 United States presidential election has been characterized as a
period of extreme divisiveness that was exacerbated on social media by the
influence of fake news, trolls, and social bots. However, the extent to which
the public became more polarized in response to these influences over the
course of the election is not well understood. In this paper we propose
IdeoTrace, a framework for (i) jointly estimating the ideology of social media
users and news websites and (ii) tracing changes in user ideology over time. We
apply this framework to the last two months of the election period for a group
of 47508 Twitter users and demonstrate that both liberal and conservative users
became more polarized over time.
