Excess supply

Also called: Glut, surplus · Topic: Markets, Equilibrium and Government Intervention · NCERT: Class 7, Ch 12 "Understanding Markets"; Class 9, Ch 9 "The Price Puzzle: What Drives the Market"; Class 12, Ch 5 "Market Equilibrium"

Meaning

Excess supply (also called a surplus or glut) happens when, at a given price, sellers want to sell more of a good than buyers want to buy.

• Formula: ES(p) = qˢ(p) − qᴰ(p) > 0
• qˢ(p) = market supply: the total quantity all firms want to sell at price p.
• qᴰ(p) = market demand: the total quantity all buyers want to buy at price p.

Excess supply appears only when the price is above the equilibrium price (p*). In a free market, it pushes the price down until the market clears. It explains why prices fall and why unsold stock builds up. It also explains what goes wrong when the government holds a price above p*.

Explanation

How excess supply arises

• Market equilibrium is the point where the plans of buyers and sellers match: qᴰ(p*) = qˢ(p*).

• At this point, excess demand and excess supply are both zero.

• If the price is set above p*:

• buyers want less, because of the law of demand (price up → quantity demanded falls)

• sellers want to sell more, because of the law of supply (price up → quantity supplied rises).

• The gap between the two is excess supply. On a graph, it is the horizontal distance between the supply curve and the demand curve at any price above the point where they cross.

Worked examples (NCERT)

Wheat market (Class 12, Example 5.1)

• Demand: qᴰ = 200 − p. Supply: qˢ = 120 + p (for p ≥ ₹10).
• Equilibrium: 200 − p* = 120 + p*, so p* = ₹40/kg and q* = 160 kg.
• Excess supply function: ES(p) = (120 + p) − (200 − p) = 2p − 80. It is positive for any p > 40.
• At p = ₹45:
• qˢ = 165 kg and qᴰ = 155 kg
• ES = 10 kg. Check: 2(45) − 80 = 10 ✔

Mango table (Class 9, The Price Puzzle)

Price (₹/kg)	Qd (kg)	Qs (kg)	Result
100	12	12	Equilibrium
150	8	43	Excess supply = 35 kg, so price falls

Guava bargaining (Class 7, Understanding Markets)

• The seller asks ₹80/kg. Buyers find this too high, so there are too few buyers at this price.
• This is excess supply in miniature. The seller must lower the price to a "just right" level.

How the market removes it: the invisible hand

• Price above p* → surplus → price falls
• Firms with unsold stock cut their prices.
• A lower price means more people buy, so quantity demanded rises.
• A lower price also means producing is less profitable, so quantity supplied falls.

• The gap closes at p*.

• Wheat example: at ₹45 there is a 10 kg surplus. As the price falls to ₹40, supply falls from 165 to 160 kg and demand rises from 155 to 160 kg.

• This self-correcting process is Adam Smith's invisible hand. He used the phrase in Wealth of Nations (1776), Book IV, Chapter 2. For Smith, competition among sellers pushes prices down to their "natural" levels, which match the costs of production [2].

What stops a surplus from clearing

• NCERT assumes that prices always adjust to equilibrium. It does not prove this.
• Clearing needs three things: prices that can move freely, competition, and good information.
• A surplus can last when:
• price controls keep the price above p*. For example, a price floor (a legal minimum price) set above equilibrium creates a lasting surplus.
• there is a monopoly (a market with a single seller)
• supply responds slowly. Farm output takes a full season, so farmers cannot cut production quickly.

In India

• Food surpluses and the poor: the Green Revolution produced foodgrain surpluses. These lowered food prices relative to other goods. This helped low-income groups, who spend a large share of their income on food.
• Farm price support: farm markets in India have few buyers, poor information and supply that reacts late. Gluts at harvest time can crash prices. This is a reason for MSP (Minimum Support Price, a price at which the government promises to buy crops) and for procurement (government buying of grain). But if the support price stays above the market price, the government buys up the surplus and stocks pile up. This is why these tools are debated.
• Foreign exchange market: the rupee's exchange rate (the price of one currency in terms of another) is now set by demand and supply.
• March 1992: the Liberalised Exchange Rate Management System (LERMS) started. It was a dual exchange rate system (two official rates at the same time) [3].
• 1 March 1993: a unified, market-determined exchange rate, based on the demand for and supply of foreign exchange, replaced LERMS [3].

• When dollars are in excess supply, their rupee price tends to fall. The RBI does not fix the rate. It buys or sells foreign currencies only to calm sharp swings and keep "orderly conditions" [3].

• Price discovery means finding the equilibrium price through trading. It removes gluts best when there are many buyers and sellers and information is shared widely (Economic Survey 2006-07) [4].

Don't confuse with

• Excess demand (shortage): qᴰ > qˢ. It happens below p* and pushes the price up. Excess supply is the opposite: it happens above p* and pushes the price down. Exam questions often swap "shortage" and "surplus".
• Equilibrium: here ES = ED = 0 and the market clears. Excess supply is by definition a situation out of equilibrium.
• Producer or consumer surplus: these measure the gain that sellers or buyers get from trade. A market "surplus" (excess supply) is a quantity of unsold goods. The word is the same, but the idea is different.
• Fall in the general price level: excess supply lowers the price of one good compared with others (its relative price). A fall in all prices together is a different, economy-wide idea.

Prelims Hooks

• Excess supply: ES(p) = qˢ(p) − qᴰ(p) > 0. It happens only when price is above p*, and the price then tends to fall.
• NCERT wheat market: qᴰ = 200 − p, qˢ = 120 + p gives p* = ₹40/kg, q* = 160 kg. ES = 2p − 80, so at ₹45, ES = 10 kg.
• Mango table (Class 9): equilibrium at ₹100/kg, 12 kg. At ₹150, Qs = 43 and Qd = 8, so the surplus is 35 kg.
• A price floor set above equilibrium causes a lasting surplus. A price ceiling set below equilibrium causes a lasting shortage. Watch for questions that swap the two.
• "Invisible hand": Adam Smith, Wealth of Nations (1776), Book IV, Chapter 2 [2].
• Rupee: LERMS (dual rate), March 1992 → market-determined unified rate from 1 March 1993. The RBI intervenes only to keep orderly conditions and has no fixed target [3].

Mains Points

• Support prices vs market clearing (GS-III):
• MSP and procurement protect farmers from harvest-time gluts. In farm markets, supply comes with a lag and there are few buyers, so prices can crash.
• But support prices kept above the market price create lasting surpluses. The government then has to buy and store the extra grain.

• The policy challenge is to protect farm incomes without creating stocks that are never used.

• Free prices as a signal:

• The move to market prices after 1991, such as the rupee from 1993, relies on prices falling when there is excess supply. Nobody has to order it [3].

• But the RBI still steps in to limit volatility. So "market-determined" in practice means managed, not left fully free [3].

• Welfare side of surpluses:

• Green Revolution surpluses lowered the relative price of food and helped the poor.
• So a surplus is not always a problem. Who gains and who loses depends on whose goods get cheaper.

Related concepts

• Market equilibrium
• Equilibrium price
• Equilibrium quantity
• Invisible hand
• Market forces
• Relative prices
• General equilibrium

Read more

• Market equilibrium, excess demand, excess supply and the invisible hand