In 1968 the Prague Spring outbreak of heretical socialism in Czechoslovakia caused the BCP to tighten control over all social organizations, calling for democratic centrism and elimination of unreliable elements from the party. This policy kept the BCP on a unified path in complete support of SovÍÍÍiet interests it also led to a new Bulgarian constitution and BCP program in 1971. Approved by the Tenth Party Congress and a national referendum, the 1971 constitution detailed for the first time the structure of the BCP (highly centralized, in keeping with policy after 1968) and its role in leading society and the state. BANU was specified as the partner of the BCP in the cooperative governing of the country. A new State Council was created to oversee the Council of Ministers and exercise supreme executive authority (see The Constitution of 1971 , ch. 4). In 1971 Zhivkov resigned as prime minister to become chairman of the State Council, a position equivalent to Bulgarian head of state. The new constitution also defined four forms of property: state, cooperative, public organization, and private. Private property was limited to that needed for individual and family upkeep.

Data as of June 1992