The boom period was from the 1950s to the 1970s, decades characterized by a stable post-war order that began with the Marshall Plan in 1947 and came to an end with the economic changes starting in 1973. Fundamental changes originated from the economy and had an impact on the political and social guiding principles in Western European countries. The societal model of the boom era transformed with high dynamics. This complex development represents a structural break in the evolution of the Federal Republic and Western Europe since World War II. The coexistence of continuity and rupture in structures and mentalities marks a new era in European history.