France emerged from the Second World War with the enormous task of reconstructing much of its public infrastructure and communications, and modernisation of old housing. Regional or national planning is mainly economic and structured around the series of four-year plans initiated in the postwar period. The overall structure of planning follows a hierarchy from national to local level, and seeks to interrelate physical planning with social and economic planning. National directions for physical planning are developed as well. The national government initiates legislation, which has to be approved by Parliament. The central element is the national plan which sets economic, social and physical planning objectives every four years. In addition to development plans and control, certain positive planning tools enable public agencies to act as developers or on the land market, and therefore complement or counteract free-market forces. Development control is often perceived by the public as the responsibility of the state.