Did Brexit Travel? Eurosceptic Parties across Europe on Facebook after the 2016 Referendum

Eurosceptic parties across Europe might be expected to have drawn attention from the United Kingdom's vote to leave the European Union on 23 June 2016. I test whether engagement with the Facebook pages of Eurosceptic parties and leaders in 19 other European countries changed around the referendum and later Brexit milestones, using CrowdTangle data. I compare 37 Eurosceptic pages, classified with the PopuList, with other pages in the same country and week in a 25-week window around the vote (42,265 posts from 143 pages). Posts mentioning Brexit or the UK rose from under 1% to about 9% of posts in the two weeks after the vote, but equally for Eurosceptic and other pages. Engagement per post did not change differentially in those two weeks (−0.02 log points, SE 0.11), nor did the mix of reactions. Eurosceptic pages posted about 16% less than other pages in those weeks, but similar dips appear in late June 2014, 2017 and 2018. Of five later milestones, only the March 2019 extension gave a clearly positive estimate, about 23%, but it does not survive clustering by country or adjustment for testing both outcomes, coincides with the European Parliament campaign, and came without more posts about Brexit. In the United Kingdom itself, interactions per post with all parties' pages roughly doubled relative to pages elsewhere. On Facebook, Brexit was a large British event and a shared topic abroad, but I find no sign that it lifted Eurosceptic parties elsewhere relative to their rivals.Preprint, not peer reviewed.