Nikolai Dmitrievich Kondratiev

In his 1925 paper 'Big Cycles of Conjuncture,' Kondratiev argued that capitalist economies trace long waves of roughly 50–60 years. Using price, interest rate, wage, trade, and output data from Britain, France, Germany, and the United States spanning the 19th and early 20th centuries, he empirically identified a wave pattern of three phases: expansion, downturn, and depression. The first two waves he identified ran 1790–1849 (turning point around 1815) and 1850–1896 (turning point around 1873); a third wave, he proposed, began around 1896.

He held that social upheavals such as wars and revolutions arise from the tensions of the ascendant phase (intensified competition for markets and raw materials) and pointed to the replacement cycle of large-scale fixed capital (canals, railways, etc.) as a causal mechanism. His theory was attacked by contemporary Marxists for allegedly denying capitalism's 'chronic crisis,' but in 1939 Joseph Schumpeter introduced the term 'Kondratieff waves' in his Business Cycles, bringing the concept into Western economics. The theory was later reassessed by Ernest Mandel, Eric Hobsbawm, and others, and continues to be debated in economic history and futures studies alongside explanations based on technological innovation clusters, demographic shifts, and credit cycles.

In 1927 criticism of Kondratiev's ideas began and quickly turned into political persecution of him as the 'ideologist of the kulaks'; on 19 April 1928 he was removed from his post. On 19 June 1930 he was arrested on the charge of creating and leading the non-existent 'Peasants' Labour Party' (Трудовая крестьянская партия), the case later known as the 'Peasants' Labour Party' affair.

On 26 January 1932 the OGPU collegium sentenced him to eight years' imprisonment, and from February he served the term in the Suzdal political isolator. In the first period of his imprisonment he continued to work actively and exchanged letters with his wife and daughter. The Suzdal Letters, published in 2004 after the dissolution of the USSR, is a volume of nearly 900 pages collecting letters to his wife, memoirs and the economic calculations he did in confinement; his letter of 11 July 1934 mentions a formula confirmed by British and American data. His health, however, worsened every year. In a letter of 29 November 1933 he contrasted his relatively cloudless early life with the blows that followed; after seven years in the political isolator he could barely see, moved with difficulty and suffered severe headaches. He wrote of four years of illness and exhaustion and of his fear of having become in large part an intellectual invalid. He nonetheless planned five new books, and his last letter, to his daughter Elena, was sent on 31 August 1938.

On 17 September 1938 the Military Collegium of the USSR Supreme Court sentenced him to be shot, and he was executed the same day. His relatives were told only that he had been condemned to 'ten years without the right to correspond with the outside world'; the execution and the Kommunarka burial place became known only much later. In prison he had also faced a second charge of leading the 'Peasants' Labour Party' and continuing counter-revolutionary activity in the Suzdal prison.

Rehabilitation came only decades later, in two stages. In May 1963 he was rehabilitated together with L. N. Yurovsky, but this was not publicised in the USSR, and Soviet economics continued to denigrate his works until 1987. A second rehabilitation, together with A. V. Chayanov, took place on 16 July 1987. A memorial plaque stands at the Spaso-Evfimiev Monastery in Suzdal, a monument was erected in his native village of Galuevskaya, and in 2013 a film-play based on his surviving notebooks of letters to his daughter was staged. His 1927 memorandum to V. M. Molotov was published in 1989.