Which one of the following is not a standard method used for the measurement of national income of a country?

Introduction / Context:
National income accounting is a core topic in macroeconomics. It deals with the measurement of the total value of goods and services produced within a country. Standard textbooks explain that there are three main methods that, in principle, should give the same estimate of national income. Examination questions often ask you to recall the names of these methods and to identify any option that does not belong to this standard list. This tests both basic memory and understanding of what each method measures.

Given Data / Assumptions:

• National income can be measured by more than one method.
• The three accepted methods are the value added (or product) method, the income method and the expenditure method.
• The term investment is part of national income accounts but is not itself the name of a complete method.
• The question asks for the option that is not a method of measuring national income.

Concept / Approach:
The value added method sums the value added by each producing unit or industry in the economy. The income method sums all factor incomes such as wages, rent, interest and profit received by residents. The expenditure method sums the expenditures on final goods and services, usually in the form of consumption, investment, government expenditure and net exports. All three methods should, in theory, give the same value for national income. Investment, however, is a single component in the expenditure method, not a fourth independent method. Therefore, any option that lists investment method as a separate method is incorrect.

Step-by-Step Solution:
Step 1: Recall the three standard methods: product or value added method, income method and expenditure method.Step 2: Match these names with the options provided.Step 3: Observe that value added method, income method and expenditure method all appear as options and are legitimate methods.Step 4: Identify investment method as the odd one out that is not recognised as a full method of national income measurement.

Verification / Alternative check:
If you check any introductory macroeconomics text, it will explain national income measurement under three headings corresponding to product, income and expenditure. You will not find a separate section called investment method. Instead, investment is included as one of the spending components under the expenditure method. This cross check confirms that investment method is not a standard name for measuring national income and therefore must be the correct choice for this question.

Why Other Options Are Wrong:
Option A is correct as a method because the value added method, also called the product method, calculates national income by summing value added at each stage of production. Option B is correct because the income method sums factor incomes. Option C is correct because the expenditure method sums total spending on final goods and services. Option D, investment method, is wrong in this context because investment is only one component of expenditure and not an independent method of measuring national income.

Common Pitfalls:
Students sometimes misinterpret the close relationship between investment and growth and assume that there must be an investment based method of calculating national income. Another error is to think that any macroeconomic term that appears in the national accounts can be used as the label for a method. To avoid such mistakes, it is important to memorise the three standard method names and remember that any fourth unfamiliar label is likely to be the incorrect option in such questions.

Final Answer:
The method that is not used as a standard way of measuring national income is the so called investment method.