The 1992-1994 parliamentary term also saw the first major change to the Italian electoral system since the late 1940s, with a 1993 referendum abolishing the clause of the electoral law which required candidates to win two-thirds of votes to be elected in the Senate's single-member districts. This essentially transformed the Senate electoral law from "de facto" pure proportional representation to a majoritarian additional member system. Parliament subsequently passed a new electoral law establishing a similar system for the Chamber of Deputies.