Abstract: Nikolai Kondratiev was one of the Russian economists whose work had most impact on the academic profession in the early twentieth century; after following courses by Tugan-Baranovsky, he joined in the development of new approaches to economic statistics.As the natural follower of Clément Juglar, who first analysed the industrial or business cycle, he led the Institute of Conjuncture in Moscow in the twenties while analysing the statistics of long cycles in prices, interest rates, and trade in the principal countries.Kondratiev was later a victim of one of the bloody purges of the Stalinist era and, after eight years in prison, was finally shot.Yet his short period in the Institute and his rare publications, some of them translated into German and then into English, became known to many western colleagues: Simon Kuznets, Wesley Mitchell, Ragnar Frisch, Jan Tinbergen, and especially Joseph Schumpeter, who named the long waves of industrial change ‘Kondratievs’ or ‘Kondratiev cycles’.Kondratiev became the only Russian-born economist to be part of the foundation of the Econometric Society in spite of living in jail at that time and his contribution, his hypotheses and statistical demonstrations, and the fierce debate with his own colleagues at the Institute are discussed in detail in this chapter.

Keywords: innovation, Joseph Schumpeter, Nikolai Kondratiev, Long Wave, prison, statistics, structural change,