Q.Assertion (A): Export is a flow variable.
Reason (R): Export depend on the size of population at a point of time.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Stock Versus Flow
Let’s start with something you already know: your pocket money.
Suppose your father gives you ₹500 every week. That ₹500 is a flow — it comes in over a period of time. Now suppose you save ₹200 each week for a month. At the end of the month, you have ₹800 in your wallet. That ₹800 is a stock — it is the amount you have at a particular point in time.
This is the whole idea in a nutshell. A stock is measured at a point in time. A flow is measured over a period of time.
The precise meaning
In economics, the distinction is crucial because it prevents confusion between what you have and what you get.
Stock — a quantity measured at a specific moment. It has no time dimension.
Flow — a quantity measured per unit of time. It has a time dimension (per day, per month, per year).
Examples from your NCERT textbook:
| Stock | Flow |
|---|---|
| Wealth | Income |
| Capital | Investment |
| Money supply (on a given date) | Money supply growth (per year) |
| Population (on 1 Jan) | Births (per year) |
| Water in a tank | Water flowing in per minute |
Notice: a stock can change only because of flows. If you add water (inflow) and remove water (outflow), the stock changes. This gives us a simple identity:
Stock at end=Stock at start+Inflow−Outflow
In national income accounting, this becomes:
Kt=Kt−1+It−Dt
Where:
- Kt = capital stock at the end of year t (a stock)
- Kt−1 = capital stock at the start of year t (a stock)
- It = gross investment during year t (a flow)
- Dt = depreciation during year t (a flow)
Why it matters
If you mix up stock and flow, you make serious errors. For example:
- “India’s national income is ₹200 lakh crore” — that’s a flow (per year).
- “India’s national wealth is ₹1,000 lakh crore” — that’s a stock (at a point).
You cannot compare them directly. A country with a high income (flow) might have low wealth (stock) if it spends everything. A rich country (high stock) might have low current income.
Another classic mistake: “Investment is part of capital.” No — investment is a flow that adds to the stock of capital. Capital is the accumulated result of past investments.
A diagram in words
Imagine a bathtub. The water level at 8:00 AM is a stock. The tap is open — water flows in at 5 litres per minute — that’s a flow. The drain is open — water flows out at 2 litres per minute — that’s another flow. The water level at 8:10 AM is a new stock, higher than before because inflow exceeded outflow.
In the economy: …
Export, being measured over a period of time, is indeed a flow variable, so the assertion is true; but the reason wrongly links it to population at a point of time, so the reason is false. …
The correct option is (c) — Assertion true, Reason false.
Assertion (A): 'Export is a flow variable.' This is true. A flow is measured over a period of time (e.g. per month or per year); exports are measured as the value of goods sold abroad during a period, so exports are a flow.
…
Showing the 12 most recent of 17 on this concept.
- CBSE 2026Set MARCH1 markMCQQ.Which one of the following is a stock variable?(a) Income(b) Expenditure(c) Capital(d) Investment
›Reveal solutionSolution
Capital is measured at a point of time, making it a stock variable, so the answer is (c).
…
- CBSE 2026Set ANNUAL1 markQ.Fill in the blank: The concept of stocks are defined at a particular ________.
›Reveal solutionSolution
A stock is defined at a particular point of time.
A stock is an economic quantity measured at a particular point of time, with no time-period dimension — for example, the stock of capital, wealth, or the quantity of money on a given date. (A flow, in contrast, is measured over a …
- CBSE 2025Set ANNUAL1 markMCQQ.Which of the following is a stock? (A) Wealth (B) Saving (C) Export (D) None of these
›Reveal solutionSolution
Wealth is a stock variable, so the answer is (A) Wealth.
The stock-flow distinction is fundamental in national income accounting. A stock has no time dimension — it is the quantity existing at a particular moment (e.g. wealth, money supply, capital). A flow is measured over an interval of time — e.g. saving per year, exports per year, income per month. Among the options, wealth is a stock, while saving (B) and export (C) a …
- CBSE 2025Set ANNUAL1 markMCQQ.Which one of the following is included in stock? (A) Quantity of money (B) Wealth (C) Quantity of wheat stored in warehouse (D) All of these
›Reveal solutionSolution
All the listed items are stocks, so the answer is (D) All of these.
A stock variable has no time dimension — it is measured at a particular moment. (A) the quantity of money in the economy at a date, (B) wealth held at a point of time, and (C) the quantity of wheat stored in a warehouse at a given moment are all measured at a point of time, hence all are stocks. (A flow, by contrast, is measured over a p …
- CBSE 2025Set ANNUAL1 markMCQQ.Flow of goods and services across different sectors of the economy is called – (A) Circular flow (B) Money flow (C) Real flow (D) Capital flow
›Reveal solutionSolution
The flow of goods and services (and the matching flow of money incomes) between households, firms and other sectors of the economy, round and round without end, is known as the circular flow of income.
In an economy, households supply factors of production (land, labour, capital, enterprise) to firms and receive factor incomes (rent, wages, interest, profit) in return. Firms use these factors to produce goods and services, which flow back to households in exchange for money payments (expenditure). This continuous, circular movement -- goods/services flowing one way and money payments flowing the other way, repeating endlessly -- is calle …
- CBSE 2024Set ANNUAL1 markMCQQ.Which of the following is a stock? (A) Wealth (B) Saving (C) Export (D) Profit
›Reveal solutionSolution
Wealth is measured at a point of time, so it is a stock — the answer is (A).
In the BSEB Inter Class-12 Economics (National Income Accounting) syllabus, a stock is a quantity measured at a particular point of time (no time dimension), while a flow is measured over a period of time. Wealth is the value of assets held at a given moment, so it is a stock. Saving (B), exp …
- CBSE 2024Set ANNUAL1 markMCQQ.Which of the following is included in stock? (A) Quantity of money (B) Wealth (C) Quantity of wheat in warehouse (D) All of these
›Reveal solutionSolution
The correct option is (D) All of these. Quantity of money, wealth, and the stock of wheat in a warehouse are each measured at a single point of time, which is exactly what defines a stock variable.
In this BSEB Class-12 Commerce Economics (national income accounting) question, we must separate a stock from a flow. A stock has no time dimension; it is measured at a point of time (e.g., on 31st March). A flow is measured over a period of time (e.g., per year).
Check each option:
- (A) Quantity of money — the money supply existing on a given date is a stock.
- (B) Wealth — the value of assets held at a point of time is a stock. …
- CBSE 2024Set ANNUAL1 markMCQQ.Which of the following is not a flow? (A) Capital (B) Income (C) Investment (D) Depreciation
›Reveal solutionSolution
The correct option is (A) Capital. Capital is a stock (held at a point of time); income, investment and depreciation are all flows measured over a period.
This BSEB Class-12 Economics question again tests the stock-versus-flow distinction. A flow variable is measured over an interval (e.g., per month or per year); a stock variable is measured at a point of time.
Examine the options:
- (A) Capital — the quantity of capital existing on a date is a stock, so it is NOT a flow.
- (B) Income — earned over a period (e.g., per year) → flow.
- (C) Investment — addition to capital stock over a period → flow. …
- CBSE 2023Set 58/3/11 markMCQQ.(i) Read the following statements carefully : Statement 1 : Stock variables are measured at a point of time. Statement 2 : Flow variables and stock variables are same. In light of the given statements, choose the correct alternative from the following : (A) Statement 1 is true and Statement 2 is false. (B) Statement 1 is false and Statement 2 is true. (C) Both Statements 1 and 2 are true. (D) Both Statements 1 and 2 are false.(OR)(ii) Identify, flow variable from the following : (Choose the correct alternative) (A) Distance between Delhi and Amritsar (B) Annual expenditure of a school (C) Bank balance of Mr. Mukesh as on 31st March, 2022 (D) Investments of Mr. Mohit as on 31st December, 2021
›Reveal solutionSolution
Part (a): Correct alternative is (A) — Statement 1 true, Statement 2 false.
Part (b): Correct alternative is (B) — Annual expenditure of a school is a flow variable.
Part (a)
The distinction between stock and flow depends on how the variable is measured over time.
- A stock variable is a quantity measured at a single point of time — a static snapshot. Examples: capital, wealth on a date, money in a bank account on a given day, national debt on 31st March.
- A flow variable is a quantity measured over an interval of time — a rate that accumulates. Examples: income per year, expenditure per month, national output per year.
Evaluating the statements:
- Statement 1 — "Stock variables are measured at a point of time." This matches the definition of a stock exactly → true.
- Statement 2 — "Flow variables and stock variables are same." They are fundamentally different: a stock changes because of flows (like the water in a tank changing due to inflow/outflow), but they are not identical → false. …
- CBSE 2023Set ANNUAL1 markQ.Define stock.
›Reveal solutionSolution
A stock is measured at a single point in time; a flow is measured over a period. Capital, wealth and the money supply on a date are stocks.
A stock variable is measured at a particular instant — for example, the capital stock, the money supply, or a person's wealth as on 31st March. It has no time period attached to it. This contrasts with a flow variable, which is measured over an interval of time (such as income per year or investment per month). A useful test: if asking 'how …
- CBSE 2022Set MARCH1 markMCQQ.Which one of the following is a Stock Variable?(a) Wealth(b) Income(c) Investment(d) GDP
›Reveal solutionSolution
Wealth is a stock variable (option a); income, investment and GDP are flows.
…
- CBSE 2022Set ANNUAL1 markMCQQ.(iii) A Quantity measured over a period of time (A) Stock (B) Flow (C) Depreciation (D) Wealth
›Reveal solutionSolution
A quantity measured over a period of time is a flow — option (B).
The distinction between stock and flow is fundamental in macroeconomics. A stock variable has no time dimension and is measured at a particular point of time (for example, the amount of water in a tank, or national wealth on 31 March). A flow variable has a time dimension and is measured per unit of time — per ho …
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