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What the subject studies, why it was born in a crisis, the four sectors that make up an economy, and the circular flow that ties them together.
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Macroeconomics is one connected argument, not six separate topics. Here is the argument.
Everything in Chapters 2–6 is a question about the circle you will draw today. If the circular flow is clear, the rest of the year is arithmetic and detail.
Micro vs macro, aggregates, the economy as a single unit.
The Great Depression of 1929 and Keynes, 1936.
Households, firms, government, external sector.
The single distinction students lose most marks on.
Drawn sector by sector — real flows, money flows, leakages, injections.
Why product = income = expenditure. The bridge into Chapter 2.
You have spent a year in microeconomics looking at one market at a time. Macroeconomics changes the lens, not the subject.
Microeconomics studies the behaviour of individual economic units — a single consumer, a single firm, a single market — and how price is determined there, assuming the rest of the economy stays unchanged.
Macroeconomics studies the economy as a whole: the aggregate economic variables — total output, total employment, the general price level — and the interlinkages between the sectors of the economy.
It is not "small things vs big things". It is what you are allowed to hold constant. Micro freezes the rest of the economy to study one market. Macro refuses to freeze anything — the interlinkages are the subject.
| Basis | Microeconomics | Macroeconomics |
|---|---|---|
| Unit of study | An individual household, firm or market | The economy as a whole |
| Variables | Price of wheat, output of one firm, wage in one industry | General price level, national income, total employment |
| Central question | How is price determined? | How is income and employment determined? |
| Also called | Price theory | Income and employment theory |
| Method | Partial equilibrium — rest of economy held constant | General equilibrium — sectors interact |
| Typical problem | Why did onion prices rise? | Why did inflation rise? |
The one idea that makes macro a separate subject rather than micro added up.
Fallacy of composition — the error of assuming that what is true for one individual must also be true for the economy as a whole.
One person stands up at a cricket match and sees better. Everybody stands up and nobody sees better — and everyone is now tired.
One family saves more and becomes richer. Every family saves more, so spending falls, so firms sell less, so they produce less and employ fewer people — and incomes fall until the country saves no more than before.
Because of the fallacy of composition, macroeconomics cannot be derived by adding up microeconomics. The whole behaves by rules of its own. That is why the subject exists.
Because your spending is my income. When every household cuts spending to save more, firms' sales fall; firms cut production and employment; incomes fall. Since saving depends on income, falling income drags saving back down — often to exactly where it started.
Classify each as a micro or a macro problem, and say why:
The test is never the size of the number. It is: is this variable an aggregate for the whole economy, or one unit inside it?
Subjects rarely appear from nowhere. This one appeared because the existing theory failed in public, for a decade, in front of everybody.
The Great Depression, 1929 — a collapse that began in the United States in 1929 and spread across the industrialised world through the 1930s.
Classical economics said that a fall in demand would simply push wages and prices down until every worker who wanted a job at the going wage found one. Markets would self-correct. Yet unemployment stayed at a quarter of the workforce for years. The prediction failed.
John Maynard Keynes, The General Theory of Employment, Interest and Money, 1936 — the book that founded macroeconomics as a separate subject.
Output and employment are determined by aggregate demand — total spending in the economy — and there is no guarantee that aggregate demand will be large enough to employ everybody. An economy can sit, quite stably, at less than full employment.
If the private sector will not spend enough, someone else must: the government, by spending more or taxing less. This is why "the government has a job to do in the economy" is a macroeconomic conclusion, not a political opinion — and it is why Chapter 5 exists.
"Output is determined by aggregate demand" is the sentence we will turn into a diagram, a schedule and a multiplier. Chapter 4 is nothing but this one claim, made precise.
"The Great Depression was simply a very large fall in the demand for goods, so microeconomics could have explained it." Do you agree? Give one reason.
No. Microeconomics explains a fall in demand for one good by people switching to another — total demand is unchanged. The Depression was a fall in demand for goods in general, with nothing to switch to. There is no "other market" to absorb the released workers, so the micro apparatus has nothing to say. Explaining a fall in aggregate demand needs a theory of the aggregate.
Macroeconomics does not track millions of people. It groups every economic agent into four sectors, each with one characteristic job.
Own the factors of production — land, labour, capital, enterprise. They supply factor services to firms, receive factor incomes, and consume and save.
Hire factors and produce. They pay factor incomes, sell goods and services, and invest — buy capital goods and add to inventories.
Taxes, spends and transfers. It buys goods and services, provides public goods, makes transfer payments, and regulates through its budget and its central bank.
Trades with us. It buys our exports, sells us imports, and capital flows in and out.
A single person can belong to more than one sector at different moments: as a worker you are a household, as a shopkeeper you are a firm. Sectors classify roles, not people.
Textbooks build the economy up one sector at a time. Know all four names.
| Model | Sectors included | What it lets you study |
|---|---|---|
| Two-sector | Households + Firms | The pure circular flow; income = output = expenditure |
| Three-sector | + Government | Taxes, government spending, the budget |
| Four-sector (open economy) | + External sector | Exports, imports, balance of payments |
Two-sector: today and Chapter 4. Three-sector: Chapter 5. Four-sector: Chapter 6. We add one sector at a time on purpose — each addition changes the answer in a way you can see.
The NCERT model assumes a capitalist economy. Four features define it — and each one is doing work in the theory.
This model captures a developed capitalist economy. India also has vast self-employment — the farmer, the shopkeeper, the artisan — who are firm and household in one person and earn mixed income, not a wage. Remember that term: it reappears in Chapter 2's income method.
Two definitions. Then a picture that makes the difference impossible to forget.
Stock — a variable measured at a point of time. It has no time dimension attached to it; you can only ask "how much, as on that date?"
Wealth · capital · money supply · population · inventory · water in a tank
Flow — a variable measured over a period of time. Its magnitude is meaningless unless you state the period.
Income · saving · investment · exports · depreciation · water flowing in per hour
Ask: "per what?" If the answer needs "per month / per year" to make sense, it is a flow. If asking "per year" makes the sentence nonsense, it is a stock.
"My income is ₹50,000" — per what? Per month. Flow.
"My wealth is ₹50,00,000 per year" — nonsense. Stock.
A stock is a reservoir of past flows. Change the flow and you change the rate at which the stock grows — you never change the stock directly.
Three flows that students routinely confuse. Definitions first, then one number line.
Gross investment — total expenditure on new capital goods and additions to inventory during a year.
Depreciation — the fall in the value of the existing capital stock during a year due to normal wear and tear and expected obsolescence.
Net investment = Gross investment − Depreciation. The genuine addition to the capital stock.
A firm's capital stock on 1 April 2025 was ₹800 crore. During 2025–26 it bought new machinery worth ₹150 crore and its existing machinery depreciated by ₹60 crore.
Find (a) gross investment, (b) net investment, (c) the capital stock on 31 March 2026, and (d) name each of these four figures as a stock or a flow.
Only ₹90 crore of the ₹150 crore spent actually made the firm bigger. ₹60 crore merely replaced what wore out. This is exactly the difference between gross and net that runs through the whole of Chapter 2 — GDP vs NDP, GNP vs NNP.
Students write "capital stock = 800 + 150 = 950", forgetting that ₹60 crore of the old stock disappeared. Add net investment to a stock, never gross.
Label each as a stock or a flow and justify in four words:
| Item | Stock / Flow | Because |
|---|---|---|
| Money supply | Stock | as on a date |
| Exports | Flow | during a year |
| Wealth | Stock | at a point of time |
| Saving | Flow | per month / year |
| Number unemployed | Stock | counted on a date |
| Losses of a firm | Flow | during the year |
| Foreign exchange reserves | Stock | held on a date |
| Distance travelled | Flow | over a journey |
Now we put the sectors together. Start with the simplest possible economy: two sectors, no government, no trade, no saving. Everything else in the course is this picture with more arrows.
Circular flow of income — the continuous, unending flow of goods and services and of money payments between households and firms, in which the money that leaves one sector as expenditure returns to it as income.
Your expenditure is somebody else's income. That is the whole diagram.
We will drop both assumptions in a few slides. They are scaffolding, not truth.
Every real flow is matched by a money flow going the other way. Goods move right-to-left; money moves left-to-right to pay for them. That is all a market is.
Real flow — the flow of factor services from households to firms and of goods and services from firms to households.
Also called the physical flow. Measured in units: hours of labour, tonnes of steel.
Money flow — the flow of factor payments from firms to households and of consumption expenditure from households to firms.
Also called the nominal flow. Measured in ₹.
In the two-sector model, three totals turn out to be exactly equal. Name them, and say which arrow of the diagram each one is measured on.
They are equal because they are the same money counted at three points of the same circle. Firms pay out as income exactly what they receive as expenditure, and what they receive as expenditure is the value of what they produced.
These are the value added, income and expenditure methods. In Chapter 2 we will do the same sum by all three and watch the three answers agree — that agreement is a check on your arithmetic and a proof of this diagram.
Now drop the scaffolding. In a real economy money leaks out of the circle and is injected back into it.
Leakage — income received by households or firms that is not passed on as expenditure on domestic output. It shrinks the flow.
Saving (S) · Taxes (T) · Imports (M)
Injection — expenditure on domestic output that does not arise out of households' current consumption spending. It expands the flow.
Investment (I) · Government spending (G) · Exports (X)
| Sector | Leakage — out of the circle | Injection — back into it |
|---|---|---|
| Households | Saving (S) — into banks | Investment (I) — by firms |
| Government | Taxes (T) | Government spending (G) |
| External | Imports (M) — ₹ go abroad | Exports (X) — ₹ come in |
The circular flow stays the same size only when what leaks out is exactly matched by what is injected back in.
More is withdrawn than put back. Spending falls → firms sell less → produce less → pay out less income. The flow contracts.
More is put back than withdrawn. Spending rises → firms sell more → produce more. The flow expands.
The identity is about totals, not pairs. S need not equal I item by item, nor T equal G, nor M equal X. Only the three-against-three sum must balance. A government running a deficit (G > T) is perfectly consistent with equilibrium if exports exceed imports by the same amount.
In the two-sector model this collapses to S = I — one of the two routes to equilibrium income we will use in Chapter 4.
For an economy (₹ crore): Saving = 400, Taxes = 300, Imports = 250, Investment = 450, Government spending = 320, Exports = 200.
(a) Is the circular flow in equilibrium? (b) If not, will income rise or fall, and by how much is the flow out of balance?
(a) No. Leakages ₹950 crore ≠ Injections ₹970 crore.
(b) Injections exceed leakages by ₹20 crore, so more is being put into the circle than
taken out. Income and output will rise until the extra income generates enough
additional saving, tax and import leakage to close the ₹20 crore gap.
Notice that here S (400) < I (450), T (300) < G (320), but M (250) > X (200). Two pairs push the flow up, one pulls it down. Why does the economy still expand?
Because only the net position matters. The trade drag of −50 is smaller than the combined push of +50 from investment and +20 from the government. Net: +20, so expansion.
What is the difference between microeconomics and macroeconomics?
Microeconomics studies the behaviour of individual economic units — a consumer, a firm, a single market — and how price is determined there, taking the rest of the economy as given. Macroeconomics studies the economy as a whole, through aggregate variables such as national income, the general price level and the level of employment, and it explicitly studies the interlinkages between sectors. Micro is therefore called price theory and macro income-and-employment theory. Because of the fallacy of composition, macro conclusions cannot be obtained by adding up micro conclusions.
What are the important features of a capitalist economy?
Describe the four major sectors in an economy according to the macroeconomic point of view.
Describe the Great Depression of 1929.
A prolonged worldwide slump beginning in the United States in 1929 and running through the 1930s. Aggregate demand collapsed; firms could not sell their output and cut production. US unemployment rose from about 3% in 1929 to about 25% in 1933, and aggregate output fell by roughly one-third. Because prevailing theory predicted that markets would clear automatically and they plainly did not, the episode led J. M. Keynes to argue in The General Theory (1936) that output and employment are governed by aggregate demand, and that state intervention may be necessary to raise it — the founding argument of macroeconomics.
Explain the concept of "leakage" and "injection" in the circular flow of income, and state the condition for the flow to remain constant.
A leakage is income withdrawn from the circular flow and not spent on domestic output — saving, taxes and imports. An injection is expenditure on domestic output arising from outside the households' consumption stream — investment, government spending and exports. The flow remains constant when S + T + M = I + G + X. If injections exceed leakages the flow expands; if leakages exceed injections it contracts.
"In the two-sector circular flow, the money flow and the real flow are equal in value." Is this statement true? Justify.
True. Every real flow is paid for by a money flow of exactly the same value moving in the opposite direction: the value of factor services supplied equals the factor payments made for them, and the value of goods and services sold equals the consumption expenditure on them. The two loops are the same transactions described in physical and in monetary terms.
We have drawn the circle. Now we measure it.
You now know that production, income and expenditure are three cuts through one circular flow. So: how large is that flow in India this year, in rupees — and which of the thousands of transactions in the economy should be counted, which double-counted, and which left out altogether?