In modern practice, the most common economic system followed by countries around the world is which of the following types of economy?

Introduction / Context:
Countries around the world adopt different economic systems to organise production, distribution, and consumption of goods and services. Classical textbooks describe pure market economies, command economies, and mixed economies as ideal types. In reality, most countries adopt a combination of market mechanisms and government intervention. This question asks which system is most commonly found in the world today.

Given Data / Assumptions:

• Pure market economies rely almost entirely on private ownership and market forces of demand and supply.
• Command economies involve central planning and state ownership of major resources.
• Mixed economies contain elements of both markets and government control.
• Modern economies generally have private sectors, public sectors, and regulations.
• The question asks for the most common system, not a theoretical extreme.

Concept / Approach:
A mixed economy is an economic system where both the private sector and the public sector play important roles. Markets allocate many resources, but the government intervenes through regulation, taxation, subsidies, public enterprises, and welfare programmes. Even economies commonly labelled as capitalist or socialist have some mix of private and public activity. Pure command economies and pure free market systems rarely exist in complete form. Therefore, when we look at actual countries such as India, the United States, and many European nations, we see mixed economies with varying balances between market and state.

Step-by-Step Solution:
Step 1: List the main economic systems: market economy, command economy, and mixed economy.Step 2: Consider whether any major country today operates as a purely free market system with no government intervention. In practice, this does not occur.Step 3: Consider whether most countries operate as pure command economies with complete central planning. This is also rare and has declined over time.Step 4: Observe that most countries have private ownership and market prices alongside taxes, regulations, public enterprises, and social welfare schemes.Step 5: Recognise that this combination is exactly what defines a mixed economy.Step 6: Conclude that the most common economic system in the world is a mixed economy.

Verification / Alternative check:
Introductory economics and civics books describe India, the United States, and most European nations as mixed economies, even though they differ in how much government intervention they use. Former command economies have also moved toward mixed systems by introducing market reforms while retaining some state control. As a result, mixed economy has become the standard descriptive term for the majority of national economic systems in the current global environment.

Why Other Options Are Wrong:
A pure command economy where the state directs all production is now rare and not the most common system, so option b is incorrect. A strictly planned socialist economy with no private ownership, option c, describes a theoretical model rather than the widespread reality. A completely free market economy with no state involvement, option d, does not exist in practice because governments always impose at least minimal regulations and taxes. A subsistence barter economy, option e, may exist in very small communities but is not representative of modern national economic systems.

Common Pitfalls:
Students sometimes think in terms of extremes and assume that if a country supports private business it must be a pure market economy, or if the government is active it must be socialist. This ignores the fact that almost all modern economies blend market and state features. To avoid confusion, it is useful to remember that mixed economy is the realistic category that includes most countries, while pure market and pure command systems are mostly theoretical benchmarks.

Final Answer:
The most common economic system in the world is a mixed economy that combines market forces with government intervention.