Which among the following is an example of a microeconomic variable studied in microeconomics rather than in macroeconomics?

Introduction / Context:
Economics is broadly divided into microeconomics and macroeconomics. Microeconomics focuses on individual economic units such as households, firms and specific markets, while macroeconomics studies the economy as a whole. Many objective questions test your ability to classify variables into these two branches. This question asks you to identify which variable is clearly microeconomic in nature.

Given Data / Assumptions:
- Four variables or concepts are listed: national income, aggregate supply, overall employment and consumers equilibrium.
- You are expected to know whether each variable relates to the entire economy or to individual decision makers.
- Microeconomic variables relate to individual markets or units, while macroeconomic variables relate to aggregates.

Concept / Approach:
National income, aggregate supply and total employment are macroeconomic aggregates. They describe overall levels of output, supply and employment for the entire economy. Consumers equilibrium, on the other hand, is a microeconomic concept that explains how an individual consumer allocates a given income across different goods to maximise satisfaction subject to a budget constraint. To answer correctly, we simply classify each option according to this micro versus macro distinction.

Step-by-Step Solution:
Step 1: Examine option A, national income. This measures the total income earned by factors of production in an economy over a period. It is clearly a macroeconomic aggregate.Step 2: Examine option B, aggregate supply. This refers to the total quantity of goods and services that firms in an economy are willing to produce at different price levels. By definition it is a macroeconomic concept.Step 3: Examine option C, employment in the whole economy. Overall employment or unemployment rates are also macroeconomic variables describing the labour market at the national level.Step 4: Examine option D, consumers equilibrium. This concept is used in microeconomics to analyse how a single consumer or a representative consumer chooses a combination of goods given prices and income, using tools like indifference curves and budget lines. It deals with individual behaviour, not aggregates.

Verification / Alternative check:
A quick check is to ask whether the variable is likely to appear in a national income accounting table or a macroeconomic policy report. National income, aggregate supply and overall employment would appear in such reports. Consumers equilibrium, however, appears in microeconomic theory chapters dealing with utility maximisation and does not usually feature in macro data. This contrast confirms that consumers equilibrium is the microeconomic variable among the four.

Why Other Options Are Wrong:
Option A is wrong as an answer because national income is a central macroeconomic indicator. Option B is wrong because aggregate supply relates to the total supply in the economy, not to an individual market. Option C is wrong because employment in the whole economy is again a macro level variable, used to study labour market trends and business cycles.

Common Pitfalls:
Some students confuse the word consumer with the idea of total consumption and quickly label it macroeconomic. However, consumers equilibrium is a specific theoretical condition about one consumer or a representative micro unit, not about consumption at the national level. Another mistake is to assume that any variable starting with aggregate must be macroeconomic, which is correct in this question but should still be checked carefully when reading other questions.

Final Answer:
The variable that is an example of a microeconomic concept is Consumers equilibrium.