Nikolai Kondratieff concluded in the 1920s that since the 1780s, Western econ- omies have generally followed a cycle of how many years?

54

Explanation:

Nikolai Kondratiev was a Soviet Union economist. He was popular for his economic cycle theory called Kondratieff Wave. This economic wave is defined as the intervals of evolution believed to correct itself. This cycle is caused due to technological invention that leads to an extended time of wealth.

According to him, this period started during the steam engine invention, from the 1780s to the 1830s. He concluded that Western economies have generally followed a cycle of forty to sixty years or to be specific fifty four years exactly.

answer; i believe that the correct answer is (d); //declaration of independence; plz check first good luck

d) in the state of iowa