Macroeconomics studies the economy as a whole: total output, income, employment, inflation, growth, and the general price level. Two habits carry across every topic below: keep aggregate (economy-wide) variables separate from individual-market variables, and trace a clear causal chain from an initial shock through to its effect on output, income, employment, or the price level. When a school of thought is involved, state its assumption about how the economy adjusts before giving its policy conclusion, since different assumptions about adjustment can explain the very same recession or inflation quite differently.
A. Foundational Concepts and National Income Accounting
A few distinctions prevent most beginner errors: stock versus flow (a stock is measured at a point in time, such as the stock of public debt; a flow is measured over a period, such as GDP), nominal versus real values (nominal is measured in current prices; real strips out the effect of price-level changes, isolating genuine quantity changes), and saving versus investment (saving is income not consumed; investment is spending on capital goods — the two are linked in macro models but are not the same act).
National income accounting measures the value of economic activity and links production, income, and expenditure together through the identity Y = C + I + G + (X − M): output/income equals consumption plus investment plus government spending plus net exports (exports minus imports). GDP can, in principle, be measured through the production approach, the income approach, or the expenditure approach, and all three should agree if the underlying data are fully consistent. Example: consumption 500, investment 100, government spending 150, exports 80, and imports 100 gives expenditure-side GDP of 730 in the same units. Key related terms: GNP/GNI adjusts for income earned by residents abroad versus foreigners domestically; the GDP deflator converts nominal GDP into real GDP; and per-capita measures divide by population to allow comparison across countries or over time. GDP is a useful but limited measure — it says little directly about income distribution, unpaid work, environmental costs, or overall wellbeing, which is why it is best treated as a measure of economic activity, not a complete welfare measure.
B. Consumption, Multiplier, and Accelerator
The consumption function describes how household consumption changes with income and other influences. In the simple Keynesian form, C = a + bYd, where a is autonomous consumption (spending that happens even with zero income), b is the marginal propensity to consume, MPC (the fraction of an extra rupee of disposable income that is spent), and Yd is disposable income. Saving is simply the part of disposable income not consumed. Example: if C = 100 + 0.8Yd and disposable income is 1,000, consumption is 900 and saving is 100. Four related ratios are worth knowing precisely: average propensity to consume (APC, total consumption divided by total income), MPC (the extra consumption from extra income), average propensity to save (APS), and marginal propensity to save (MPS) — and MPC plus MPS always equal 1, since every extra rupee of disposable income is either spent or saved.
The multiplier explains how an initial change in autonomous spending can produce a larger total change in equilibrium income, because one person’s spending becomes another person’s income, which is partly spent again, and so on through repeated rounds. In the simplest closed model with no taxes or imports, the spending multiplier equals 1/(1 minus MPC). Example: if MPC = 0.8, the multiplier is 5, so an initial autonomous increase of 10 can, under the model’s assumptions, raise equilibrium income by 50. Leakages such as saving, taxes, and imports reduce the size of the multiplier in richer, more realistic models, because each leakage removes some spending from continuing around the circular flow. The multiplier is a model relationship built on stated assumptions, not a guaranteed real-world outcome, and this caveat is worth stating explicitly in an answer.
The accelerator is a related but distinct idea: rather than moving from spending to income like the multiplier, it links changes in demand or output to induced investment, because firms may need more capital when expected production rises. Example: if firms need Rs 3 of capital for every Rs 1 of annual output capacity, a sustained increase in desired output requires additional investment to expand capacity accordingly. The accelerator’s real-world strength is limited by spare capacity (firms with idle capacity may not need new investment at all), expectations (investment responds to expected, not just current, demand), finance constraints, and available technology.
C. Aggregate Demand and the Labour Market
Aggregate demand is total planned spending on domestically produced final goods and services at different price levels, and it has the same four components as the national-income identity in Section A: consumption, investment, government purchases, and net exports. Its curve slopes downward against the price level, and it can shift for reasons distinct from a change in the price level itself: a fall in interest rates may encourage both investment and some consumption, shifting aggregate demand rightward, other things unchanged; changes in expectations, fiscal policy, foreign income, and exchange rates can shift it as well. This is the same movement-versus-shift discipline from microeconomics, now applied to the whole economy.
The labour market connects employers seeking workers with people offering their labour, and unemployment means people who are able and willing to work at prevailing wages and conditions cannot find work, under whatever statistical definition is being used. Three standard categories: frictional unemployment (short-term, arising from the normal process of matching workers to jobs), structural unemployment (a mismatch between workers’ skills or location and available jobs), and cyclical unemployment (caused by a downturn in overall economic activity). Example: a recession can reduce firms’ sales and therefore their demand for labour, producing cyclical unemployment even though the affected workers’ underlying skills have not changed at all — the cause lies in demand conditions, not in the workers themselves. Labour demand depends on worker productivity and demand for the final product being produced (the same derived-demand logic covered in the microeconomics section); labour supply depends on wages, demographics, preferences, skill levels, and labour-market institutions.
D. Competing Schools on Equilibrium Income and Output
Different schools of macroeconomic thought offer different explanations for how, or whether, an economy reaches full-employment output, and it helps to compare them along the same dimensions: their core assumption about how prices and wages adjust, what they see as the cause of unemployment, and their preferred policy response.
- The classical view emphasizes flexible prices and wages that adjust to clear markets on their own, so unemployment above the natural rate is seen as temporary, and markets are trusted to self-correct without active government intervention.
- The Keynesian view allows for demand deficiency and prolonged unemployment, because prices and especially wages may be sticky (slow to adjust downward), so a shortfall in aggregate demand can persist and requires active government policy to close the gap.
- Monetarist and new-classical approaches place stronger emphasis on the role of money supply, on expectations (particularly whether they are formed rationally), and on the economy’s own capacity to adjust, generally favoring rules-based rather than discretionary policy.
Example: a Keynesian description of a recession centers on inadequate aggregate demand keeping output below its potential level; a classical account instead gives greater weight to price and wage adjustment eventually restoring equilibrium on its own, with less need for active intervention. These are broad families of thought, not single, identical models, and it is worth remembering that within each family there is real variation.
E. Inflation
Inflation is a sustained increase in the general price level, which reduces the purchasing power of money — the same amount of money buys progressively less over time. Three broad sources are worth distinguishing: demand-pull inflation (aggregate demand outpacing the economy’s productive capacity), cost-push inflation (rising input costs, such as wages or imported raw materials, pushing up prices), and expectations-related pressures (if people expect prices to rise, they may act in ways — demanding higher wages, raising prices pre-emptively — that help bring that inflation about). Very rapid money-supply growth can be inflationary, particularly over the longer run, but real-world inflation episodes often also reflect supply shocks, exchange-rate depreciation (which raises the domestic price of imports), and administered or regulated prices, so a single-cause explanation is rarely the full picture. Example: if a broad price index rises from 200 to 210 over a period, the measured inflation rate over that interval is 5%. Headline inflation measures can differ depending on which price index is used and which goods are included, which is why the specific index behind any inflation figure should always be identified rather than assumed.
Macroeconomics key takeaways: keep stocks distinct from flows and nominal from real values throughout, since most beginner errors trace back to blurring one of these pairs. The national-income identity, Y = C + I + G + (X minus M), is the accounting skeleton that every other macro topic in this paper attaches to. The multiplier and accelerator are two different mechanisms — one running from spending to income, the other from output changes to induced investment — and neither is a guaranteed real-world outcome outside its stated model assumptions. Unemployment has frictional, structural, and cyclical causes that call for different policy responses. Different schools of thought disagree mainly about how quickly and how completely prices and wages adjust, and that single assumption drives most of their other disagreements. Inflation can arise from demand, cost, or expectations channels, often in combination, so a full explanation of any real inflation episode usually draws on more than one of these.