Aggregate Demand and Its Components
Class 12 Macro Economics — What is total planned spending in an economy? Let's break it down simply.
In Simple Words
Think of the economy like a bathtub 🛁
Water flowing in from the tap = production (businesses making goods). Water draining out through the plug = spending (people buying things). The water level in the tub = national income.
If people spend as much as what's being produced, the water level stays steady (economy is stable). If they spend less (saving), water collects — but that stored water can be used by someone else (investment). Aggregate Demand is simply: “How much water is everyone trying to drain out?”
4
Groups that spend money
1
Simple formula: AD = C + I + G + (X − M)
Planned
AD = what people plan to spend, not what they actually spend
So What Exactly is Aggregate Demand?
Aggregate = Total / Everything combined. Demand = How much people want to buy.
Aggregate Demand = Total planned spending in the entire economy.
Planned ≠ Actual
AD vs Market Demand
Aggregate demand:"How much is everyone in the country planning to spend on everything?"
Samosa demand = microeconomics. Total spending = macroeconomics.
Four Groups → Four Types of Spending
Click any card to expand. Click again to collapse.
The Four Components — Closer Look
Let's look at each type of spending more carefully. Click any card to expand.
AD = C + I + G + (X − M)
The complete formula — all four groups together
Simplifying: A Two-Sector Economy
Imagine a village with only two groups — farmers (households) and a sugar mill (firm). No government collects tax. No one trades with outsiders.
The farmers earn income from the mill, spend some on food and clothes (C), and the mill spends on new crushers (I). That's it. This is a two-sector economy.
We remove G and (X−M) to understand the core relationship first. We'll add them back later.
Two-Sector Model
| Income (Y) (₹ cr) | Consumption (C) (₹ cr) | Investment (I) (₹ cr) | AD = C+I (₹ cr) |
|---|---|---|---|
| 0 | 40 | 20 | 60 |
| 100 | 120 | 20 | 140 |
| 200 | 200 | 20 | 220 |
| 300 | 280 | 20 | 300 |
| 400 | 360 | 20 | 380 |
| 500 | 440 | 20 | 460 |
| 600 | 520 | 20 | 540 |
Graph: When income is ₹200 crore
How to read this graph:
- • Dashed amber line = Consumption (C) — what households spend at each income level
- • Solid blue line = AD (C+I) — total spending, which is C plus ₹20 cr fixed investment
- • Dotted grey line = 45° line (Y=C+S) — income = spending line (for reference)
- • Drag the slider below the graph to see values at different income levels
- • The AD line is parallel to the C line because I is fixed (always ₹20 cr more)
← Less income · Drag to see spending at each level · More income →
Households spend (C)
₹200 cr
Businesses invest (I)
₹20 cr
Total AD = C + I
₹220 cr
What this tells us: At income ₹200 cr, households plan to spend ₹200 cr (consumption) and businesses plan to invest ₹20 cr. Total planned spending = ₹220 cr. At this point, C = Y (break-even). People spend everything they earn — saving is ₹0.
Key Points to Remember
Click through — each point builds on the last:
AD = C + I (in our simplified model)
For now, we ignore government and foreign trade. Total planned spending = what households spend + what businesses invest.
Summary
Key Takeaways
- AD = total planned spending in the economy. It's a flow concept (measured over a year).
- Full formula: AD = C + I + G + (X − M). Four groups — households, firms, government, foreign sector.
- Simplified (two-sector): AD = C + I. We drop G and (X−M) to focus on the core relationship.
- The AD curve starts above zero (autonomous consumption ₹40 cr + autonomous investment ₹20 cr = ₹60 cr at Y=0).
- AD curve slopes upward — as income rises, people spend more (but they also save some, so the increase is less than the income increase).
- Investment (I) is assumed autonomous — fixed at ₹20 cr regardless of income level.