CDS Economics · Microeconomics — Demand, Supply and Market Structure
Supply, Elasticity and Market Price
The inputs a producer needs, what moves supply, how elasticity measures the response to price, how demand and supply settle the price, and where markets go wrong.
Why this matters
Eight CDS questions, two of them HARD and both from CDS 2024 (I). The hard ones test special cases: a perfectly elastic supply curve and a good with a spill-over benefit, so learn the extreme curves and not only the normal ones.
Concept 1 of 4: Factors of production and capital
To make anything you need a place to work, people to do the work, things to work with, and the skill to do it well. NCERT's village of Palampur groups these into land, labour, physical capital and human capital. Physical capital is everything man-made that goes into production, whether it lasts for years or is used up at once.
Definition
The four requirements of production (NCERT Class 9):
- Land and other natural resources.
- Labour: people who do the work.
- Physical capital: all man-made inputs needed at every stage of production, made of two parts.
- Fixed capital (part of physical capital): tools, machines and buildings, used over many years.
- Working capital (part of physical capital): raw materials and money in hand, used up in one round of production.
- Human capital: the knowledge and skill (enterprise) that puts the other three together.
- Non-farm activities (small manufacturing, shops, transport) need little land, unlike farming.
| Input | Examples |
|---|---|
| Fixed capital | Tools, machines, buildings |
| Working capital | Raw materials, money in hand |
| Physical capital | Fixed capital and working capital together |
| Human capital | Knowledge, skill and enterprise of people |
| Land | The input non-farm activities need leastQ CDS 2022 (I): land is required in less quantity in non-farming activities. |
Practice this conceptself-check · 3 quick reps
The same idea in a real exam question:
CDS · 2022 · CDS (I) 2022 — General Knowledge · Q40Moderate
Example 1 · Microeconomics — Demand, Supply and Market Structure · Supply, Elasticity and Market Price
Which one of the following terms denotes the inputs in terms of tools, machines, buildings, raw materials and money in hand required at any stage of production ?
Physical capital is the whole, not one part
Tools, machines and buildings are fixed capital; raw materials and money in hand are working capital. A list that holds both kinds is physical capital.
Concept 2 of 4: Supply and price elasticity
Sellers offer more when the price rises, because producing pays better. Elasticity measures how strongly a quantity reacts to a price change: a big reaction is elastic, a small one inelastic. Two extremes matter. If the amount simply cannot change, the curve is a vertical line. If sellers will supply any amount at one price, the curve is a flat line.
Definition
Supply and elasticity:
- Law of supply: other things constant, a higher price brings a larger quantity supplied. The supply curve slopes upward.
- Supply also rises when input prices fall (cost falls), when technology improves, or when the prices of other goods the firm could make fall (resources move to this good).
- Price elasticity = percentage change in quantity divided by percentage change in price.
- Greater than 1: elastic. Less than 1: inelastic. Equal to 1: unit elastic.
- Perfectly inelastic (elasticity 0): quantity fixed whatever the price, a vertical curve.
- Perfectly elastic (elasticity infinite): any quantity at one price, a horizontal curve.
Price elasticity
- price elasticity of demand or of supply (demand elasticity is read without its minus sign)
Worked example
The price of a pen rises from ₹10 to ₹12, and the quantity demanded falls from 100 pens to 90. Find the price elasticity of demand and say whether demand is elastic.
Practice this conceptself-check · 5 quick reps
The same idea in a real exam question:
CDS · 2019 · CDS (I) 2019 — General Knowledge · Q25Moderate
Example 2 · Microeconomics — Demand, Supply and Market Structure · Supply, Elasticity and Market Price
When some goods or productive factors are completely fixed in amount, regardless of price, the supply curve is
Vertical is inelastic, horizontal is elastic
A vertical curve means quantity cannot change at all: elasticity zero, perfectly inelastic. A horizontal curve means any quantity at one price: elasticity infinite, perfectly elastic. Students often swap the two.
A cheaper other good raises this good's supply
If another good the firm could make becomes cheaper, making it pays less, so the firm moves its resources to this good and its supply rises.
Concept 3 of 4: Market equilibrium and price controls
In a free market the price is not set by anyone. It settles where the amount buyers want equals the amount sellers offer. If the price is too high, unsold goods pile up and sellers cut it; if it is too low, buyers queue and the price rises. The government sometimes overrides this with a legal minimum or maximum price.
Definition
How the market price works:
- Price mechanism: in a free market, price is set by the interplay of demand and supply.
- Equilibrium: where quantity demanded equals quantity supplied. Above it there is a surplus; below it a shortage.
- Price floor: a legal minimum price, set above equilibrium. Examples: Minimum Support Price (MSP) for crops, minimum wage.
- Price ceiling: a legal maximum price, set below equilibrium. Examples: ration shop prices, the Maximum Retail Price (MRP).
- With a horizontal (perfectly elastic) supply curve, a shift in demand changes only the quantity, never the price.
- With a vertical (perfectly inelastic) supply curve, a shift in demand changes only the price.
| Case | Result |
|---|---|
| Price floor | Legal minimum, for example MSP for cropsQ CDS 2019 (II): MSP for jowar is a price floor; MRP is a ceiling. |
| Price ceiling | Legal maximum, for example ration shop prices |
| Free-market price mechanism | Price set by the forces of demand and supplyQ CDS 2019 (II): the working of the price mechanism is the interplay of demand and supply. |
| Demand falls, supply perfectly elastic | Quantity falls, price unchangedQ CDS 2024 (I), a HARD question. |
| Demand rises, supply perfectly inelastic | Price rises, quantity unchanged |
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
CDS · 2019 · CDS (II) 2019 — General Knowledge · Q88Moderate
Example 3 · Microeconomics — Demand, Supply and Market Structure · Supply, Elasticity and Market Price
Which one of the following is an example of a price floor ?
Floor is a minimum, ceiling is a maximum
A floor stops the price falling (MSP, minimum wage). A ceiling stops it rising (ration shop prices, MRP). The words describe the limit, not the level of the price.
Flat supply absorbs the shift in quantity
If supply is perfectly elastic (horizontal), a fall in demand cuts the quantity and leaves the price where it was. Options that change the price are wrong.
Concept 4 of 4: Externalities and market failure
Sometimes an activity touches people who are not part of the deal. A factory's smoke harms neighbours who are never paid; a vaccinated child protects classmates who never paid for the shot. The market counts only the buyer's and seller's gains and costs, so it makes too much of the harmful thing and too little of the helpful one.
Definition
The ideas:
- Externality: a cost or benefit falling on people outside the transaction.
- Negative externality (pollution, overgrazing): social cost is more than private cost, so the market over-produces. Remedies: a tax or cap and trade of pollution permits.
- Positive externality (vaccination, education): social benefit is more than private benefit, so the market under-produces. Remedy: a subsidy equal to the gap between social and private benefit at the best output.
- Tragedy of the commons: a shared resource with free access (a pasture, a fishing ground) is overused, a classic negative externality.
- Public goods (street lights, national defence) are non-rival and non-excludable, so private firms under-supply them.
| Case | What the free market does |
|---|---|
| Negative externality, such as factory smoke | Over-produces |
| Positive externality, such as vaccination | Under-producesQ CDS 2024 (I): the statement that is NOT correct says the market over-produces a good with a positive externality. |
| Shared pasture with free access | Overuses it: the tragedy of the commons |
| Public good, such as a street light | Supplies too little or none |
Practice this concept4 quick reps
The same idea in a real exam question:
CDS · 2024 · CDS (I) 2024 — General Knowledge · Q69Hard
Example 4 · Microeconomics — Demand, Supply and Market Structure · Supply, Elasticity and Market Price
Which one of the following statements is not correct?
Positive externality means too little, not too much
A spill-over benefit is not paid for, so buyers buy less than society would want: the market under-produces. Over-production goes with a spill-over cost.
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Formulas (1)
- Supply and price elasticity
Price elasticity
Reference tables (3)
Factors of production and capital5 rows
| Input | Examples |
|---|---|
| Fixed capital | Tools, machines, buildings |
| Working capital | Raw materials, money in hand |
| Physical capital | Fixed capital and working capital together |
| Human capital | Knowledge, skill and enterprise of people |
| Land | The input non-farm activities need leastQ CDS 2022 (I): land is required in less quantity in non-farming activities. |
Market equilibrium and price controls5 rows
| Case | Result |
|---|---|
| Price floor | Legal minimum, for example MSP for cropsQ CDS 2019 (II): MSP for jowar is a price floor; MRP is a ceiling. |
| Price ceiling | Legal maximum, for example ration shop prices |
| Free-market price mechanism | Price set by the forces of demand and supplyQ CDS 2019 (II): the working of the price mechanism is the interplay of demand and supply. |
| Demand falls, supply perfectly elastic | Quantity falls, price unchangedQ CDS 2024 (I), a HARD question. |
| Demand rises, supply perfectly inelastic | Price rises, quantity unchanged |
Externalities and market failure4 rows
| Case | What the free market does |
|---|---|
| Negative externality, such as factory smoke | Over-produces |
| Positive externality, such as vaccination | Under-producesQ CDS 2024 (I): the statement that is NOT correct says the market over-produces a good with a positive externality. |
| Shared pasture with free access | Overuses it: the tragedy of the commons |
| Public good, such as a street light | Supplies too little or none |
Watch out for (6)
- Physical capital is the whole, not one part→ Factors of production and capital
- Vertical is inelastic, horizontal is elastic→ Supply and price elasticity
- A cheaper other good raises this good's supply→ Supply and price elasticity
- Floor is a minimum, ceiling is a maximum→ Market equilibrium and price controls
- Flat supply absorbs the shift in quantity→ Market equilibrium and price controls
- Positive externality means too little, not too much→ Externalities and market failure
Test yourself on Microeconomics — Demand, Supply and Market Structure
15 past CDS questions from this chapter, timed at 15 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.