  Social media has played an important role in shaping political discourse over
the last decade. At the same time, it is often perceived to have increased
political polarization, thanks to the scale of discussions and their public
nature.
  In this paper, we try to answer the question of whether political
polarization in the US on Twitter has increased over the last eight years. We
analyze a large longitudinal Twitter dataset of 679,000 users and look at signs
of polarization in their (i) network - how people follow political and media
accounts, (ii) tweeting behavior - whether they retweet content from both
sides, and (iii) content - how partisan the hashtags they use are. Our analysis
shows that online polarization has indeed increased over the past eight years
and that, depending on the measure, the relative change is 10%-20%. Our study
is one of very few with such a long-term perspective, encompassing two US
presidential elections and two mid-term elections, providing a rare
longitudinal analysis.
