Which of the following is NOT a main type of economic system?

The answer identifies "Blockchain economy" as not being a main type of economic system, which is accurate. Traditional economies, mixed economies, and command economies are all established classifications of economic systems used to describe how societies organize the production and distribution of goods and services.

A traditional economy relies on customs and traditions to make economic decisions, often based on agriculture or hunting and gathering. A command economy is characterized by government control over production and resource distribution, with centralized planning dictating economic activities. A mixed economy combines elements of both command and market economies, featuring both private enterprise and government intervention.

On the other hand, a blockchain economy, while it may involve the use of blockchain technology for economic transactions, does not represent a comprehensive system of economic arrangement like the others. It is more of a technological framework within which economic transactions can occur but does not itself define how resources are allocated or how goods and services are produced on a broader societal level. Therefore, it does not fall into the category of main economic systems as recognized in economic literature.