Q.[For External Candidates Only] What is positive externality? Give an example.

Price Ceiling Effects

The Everyday Intuition

Imagine a city where the rent for a one-room apartment has shot up to ₹15,000 per month. Many families can't afford it. The government steps in and says: "No landlord can charge more than ₹5,000 per month for such an apartment." Sounds like a great deal for tenants, right?

But here's the catch — at ₹5,000, everyone wants an apartment. At the old price of ₹15,000, only those who could afford it were in the market. Now, suddenly, there are far more people wanting apartments than there are apartments available. What happens next?

Some landlords might stop renting altogether (why bother for ₹5,000?). Others might ask for "key money" under the table. Many apartments might fall into disrepair because landlords can't recover maintenance costs. The well-intentioned law creates a mess.

That's the paradox of price ceilings — they help some people in the short run, but often create bigger problems.

The Precise Meaning

A price ceiling is a legal maximum price that sellers can charge for a good or service. The government sets it below the market equilibrium price — that's the key. If the ceiling is set above equilibrium, it has no effect at all.

The NCERT textbook (Class 12, Microeconomics, Chapter 5) defines it clearly: "Price ceiling means the maximum price of a commodity that the sellers can charge from the buyers."

Why It Matters: The Core Effects

When a price ceiling is imposed below equilibrium, three things happen:

1. Shortage (Excess Demand)

At the ceiling price, quantity demanded exceeds quantity supplied. The market wants more than producers are willing to provide.

2. Black Markets

Since the legal price is too low, sellers find ways to charge more illegally. This is called a black market or parallel market. The actual transaction price ends up higher than the ceiling.

3. Non-Price Rationing

Since price can't do its job of rationing the scarce good, other methods emerge:

• Queues (waiting in long lines)
• Favouritism (selling to friends and relatives)
• Lottery systems
• First-come-first-served

A Diagram in Words

Draw a standard demand-supply graph. The demand curve slopes downward, the supply curve slopes upward. They intersect at equilibrium price $P_e$ and quantity $Q_e$.

Now draw a horizontal line at price $P_c$ (the ceiling) below $P_e$.

• At $P_c$, the demand curve shows quantity demanded $Q_d$ (to the right of $Q_e$).
• At $P_c$, the supply curve shows quantity supplied $Q_s$ (to the left of $Q_e$).

The gap between $Q_d$ and $Q_s$ is the shortage. The actual quantity traded in the legal market is only $Q_s$ — because that's all producers are willing to supply.

Real-World Examples from NCERT

The textbook discusses two classic cases: …