The dataset provides data on party system change in the 15 Italian Ordinary Statute Regions (OSRs) for the 1995-2015 period. The following 10 indicators are taken into account: Total number of Lists (TL); Number of effective parties in terms of votes (NEPv); Number of effective parties in terms of seats (NEPs); Standard Innovation Rate (SIR), Effective Innovation Rate (EIR); Total electoral Volatility (TV); Total Mergers (TM); Total Splits (TS); Bipolarism Index (BPL); Bipartitism Index (BPT). The dataset covers the entirely the period of the so-called Italian Second Republic (1992-2013), namely the period following the judicial inquiry Clean Hands, which caused the implosion of the previous party system. Although the end of the Second Republic is still disputed, we consider the electoral earthquake of the 2103 at the national level (Chiaramonte and De Sio 2013; Itanes 2013) to be another turn around as far as party system change is concerned. Altogether 14 elections are taken into account and grouped in electoral cycles as follows: first cycle 1990 (elections May 6, 1990); second cycle 1995 (April 23, 1995); third cycle 2000 (April 16, 2000 and November 11, 2001); fourth cycle 2005 (April 3, 2005, April 17, 2005 and November 5, 2006); fifth cycle 2010 (December 14, 2008; March 28, 2010; and October 16, 2011); sixth cycle 2015 (February 24, 2013; November 17, 2013; May 25, 2014; November 23, 2014; and May 31, 2005).

Regional Elections in Italian Ordinary Regions during 1995-2015 period

Each election held in Ordinary Regions has been included