 Germany has protected shelters for 3% of its population, Austria for 30%, Finland for 70%, Sweden for 81%, and Switzerland for 114%.Switzerland built an extensive network of fallout shelters, not only through extra hardening of government buildings such as schools, but also through a building regulation requiring nuclear shelters in residential buildings since the 1960s (the first legal basis in this sense dates from 4 October 1963).Later, the law ensured that all residential buildings built after 1978 contained a nuclear shelter able to withstand a blast from a 12 megaton explosion at a distance of 700 metres.