Kondratieff cycle

50-year cycle of economic upturn and downturn. At the beginning of the 20th century, Russian economist Nikolai Kondratieff proposed that, in addition to the commonly accepted five- to ten-year cycle, there existed a longer cycle of about 50 years. Dismissed at the time, the theory has been re-evaluated in the light of the depressions of the 1880s and 1930s and the recessions between 1970 and the mid-1990s. It is thought that these longer cycles, if they do exist, are related to major technological change and the turmoil that follows.