Table 1. Description of Twitter data set.

Time stamps in Euro14 and Italy are in local time while time stamps in Bulgaria13 are in Greenwich Mean Time (GMT). There is a three-hours difference between GMT and Bulgarian time. T _i represents the initial day of considered data. T _e is the election day. T _f represents the final day of considered data. One-day is defined a time interval from 00:00:00 to 23:59:59 in considered time. N _T represents the total number of considered tweets for given time interval from T _i to T _e-1 posted in local language. N _P represents the number of considered political parties.

Data set	T i	T e	T f	N T	Language	N P	Held in
Euro14	22 Apr. 2014	25 May 2014	12 Jun. 2014	3,413,214	Italian	7	Italy
Italy13	1 Jan. 2013	23 Feb. 2013	3 Mar. 2014	3,796,754	Italian	6	Italy
Bulgaria13	29 Apr. 2013	12 May 2013	27 May 2013	5,817	Bulgarian	4	Bulgaria