a Russian economist

Nikolai Kondratieff was a Russian economist who is best known for suggesting that capitalist economies experience long-term cycles of boom that are followed by a cycle of depression; the cycles are now referred to as “Kondratieff Waves” or “K-waves.”

a Soviet economist

Nikolai Dmitriyevich Kondratiev (also Nikolay Kondratev or Kondratieff; Russian: Николай Дмитриевич Кондратьев) (March 4, 1892 – 1938) was a Soviet economist.