What is "scorporo"

Scorporo is a mixed member electoral system (sometimes referred to as an additional member system) whereby a portion of members are elected in single member districts (SMDs) and a portion are elected from a list. It may be fully defined as a parallel voting system, but which excludes a portion (up to 100%) of the SMD winners' votes in electing the proportional tier to result in a more proportional outcome. The exclusion of a portion of the SMD winners' votes is what makes scorporo fundamentally different from parallel voting and somewhat closer to mixed member proportional representation, and thereby between the two in terms of proportionality. The system is only known to have been used in Italy and for a portion of the compensatory tier of the National Assembly of Hungary.