Kondratiev wave

In economics, Kondratiev waves (also called supercycles, great surges, long waves, K-waves or the long economic cycle) are hypothesized cycle-like phenomena in the modern world economy. The phenomenon is closely connected with the technology life cycle.

It is stated that the period of a wave ranges from forty to sixty years, the cycles consist of alternating intervals of high sectoral growth and intervals of relatively slow growth.

Long wave theory is not accepted by most academic economists.^{[better source needed]} Among economists who accept it, there is a lack of agreement about both the cause of the waves and the start and end years of particular waves. Among critics of the theory, the consensus is that it involves recognizing patterns that may not exist (apophenia).

The Soviet economist Nikolai Kondratiev (also written Kondratieff or Kondratyev) was the first to bring these observations to international attention in his book The Long Waves in Economic Life (1926) alongside other works written in the same decade. In 1939, Joseph Schumpeter suggested naming the cycles "Kondratieff waves" in his honor. The underlying idea is closely linked to organic composition of capital.

Two Dutch economists, Jacob van Gelderen and Salomon de Wolff, had previously argued for the existence of 50- to 60-year cycles in 1913 and 1924, respectively.

Since the inception of the theory, various studies have expanded the range of possible cycles, finding longer or shorter cycles in the data. The Marxist scholar Ernest Mandel revived interest in long-wave theory with his 1964 essay predicting the end of the long boom after five years and in his Alfred Marshall lectures in 1979. However, in Mandel's theory long waves are the result of the normal business cycle and noneconomic factors, such as wars.

In 1996, George Modelski and William R. Thompson published a book documenting K-Waves dating back to 930 AD in China. Separately, Michael Snyder wrote: "economic cycle theories have enabled some analysts to correctly predict the timing of recessions, stock market peaks and stock market crashes over the past couple of decades".

The historian Eric Hobsbawm also wrote of the theory: "That good predictions have proved possible on the basis of Kondratiev Long Waves—this is not very common in economics—has convinced many historians and even some economists that there is something in them, even if we don't know what".