Electoral Volatility
Defined as “the net change within the electoral party system resulting from individual vote transfers”, electoral volatility is measured according to the following formula: TEV=Σ|Vi,t-1-Vi,t|/2, in which Vi,t is the vote share for a party ith at a given election (t) and Vi,t-1 is the vote share of the same party ith at the previous elections (t-1) (see Pedersen, 1979; Casal Bértoa, 2013: 416-418). For more details on how to calculate electoral volatility, see video. 
Please cite the following database as: Casal Bértoa, F. (): Database on WHO GOVERNS in Europe and beyond, PSGo. Available at: whogoverns.eu