Law of supply, individual supply and market supply

Detail

1. What "supply" means

• Quantity supplied is the amount of a good that a seller is willing and able to sell at a given price, in a given period.
• Supply is the whole list of those amounts at different prices. It can be shown as a supply schedule (a table) or a supply curve (a graph).
• Supply curve: a graph of how the product's price relates to the quantity sellers are willing and able to supply. Price goes on the vertical (Y) axis and quantity on the horizontal (X) axis. In most cases the curve rises from left to right, because price and quantity supplied move together [2].

2. Law of supply

• Law of supply: other things staying the same, price and quantity supplied are directly related. When the price rises, quantity supplied rises. When the price falls, quantity supplied falls.
• This is why the supply curve slopes upward. Producers are willing to sell more when the market price is higher [2].
• Class 9 gives two reasons:
• Reason 1: higher profitability. Existing producers make more output.
  • The Class 12 logic underneath is rising marginal cost (MC). MC is the extra cost of producing one more unit.
  • As output grows, MC rises. So each extra unit is worth producing only if the price is higher.
  • A competitive firm produces where price = MC, on the rising part of the MC curve. So a higher price means a higher profit-maximising output.

• Reason 2: new firms enter. A higher price attracts new firms into the market, so total supply rises.

• "Other things staying the same" (ceteris paribus). The law holds only when the other factors that affect supply stay fixed. These factors are: the number of sellers, technology, production costs, sellers' price expectations and prices of related products. If any one of them changes, the whole supply curve shifts [2].

• Movement along the curve: only the good's own price changes. This is a change in quantity supplied.
• Shift of the curve: a non-price factor changes. This is a change in supply.
• Example: more mango sellers arrive → the curve shifts right. A price rise from ₹50 to ₹100 → the market moves along the same curve.

3. Individual supply

• Individual supply is the quantity that one particular seller offers at different prices.
• Class 9 example, mango seller A:

Price (₹/kg)	Quantity supplied by A (kg)
50	1
100	2
150	3

• If you plot these points, you get an upward-sloping individual supply curve (Fig 9.4).
• Class 12 link: under perfect competition, a firm's supply curve is the rising part of its MC curve above minimum AVC (average variable cost). Below minimum AVC the firm shuts down and supplies 0. That price is called the shut-down price.

4. Market supply (Class 9, Table 9.2)

• Market supply is the total quantity offered by all sellers in the market at each price.

Price (₹/kg)	Seller A	Seller B	Seller C	Market supply (kg)
50	1	3	2	6
100	2	4	6	12
150	3	7	8	18

• Check at ₹100: 2 + 4 + 6 = 12 kg.
• Seasonal mango story:
• Start of the season: few mangoes arrive, so supply is low → mangoes are costly.
• Mid-season: many mangoes arrive, so supply has increased → prices fall.
• Note: this is a shift of supply to the right (more produce reaches the market). It is not a movement along the curve.

5. Market supply curve: horizontal summation

• Market supply curve: shows the total output of all firms at each price.
• It is built by horizontal summation. Fix a price, then add the quantities of all firms at that price. You add along the X-axis (quantity), not the Y-axis (price).
• It is drawn for a fixed number of firms.
• More firms → the market supply curve shifts right.

• Fewer firms → it shifts left.

• Short cut for identical firms: if there are n identical firms, market supply = n × one firm's supply.

6. Kinked market supply (Class 12 algebra)

• Firm 1: S₁ = 0 if p < 10; S₁ = p − 10 if p ≥ 10.
• Firm 2: S₂ = 0 if p < 15; S₂ = p − 15 if p ≥ 15.
• Market supply Sm = S₁ + S₂:
• Sm = 0 for p < 10. Neither firm produces.
• Sm = p − 10 for 10 ≤ p < 15. Only firm 1 produces.

• Sm = (p − 10) + (p − 15) = 2p − 25 for p ≥ 15. Both firms produce.

• Continuity check: at p = 15, the first formula gives 15 − 10 = 5, and the second gives 2(15) − 25 = 5. Both match.

• Worked example: at p = 20, S₁ = 10 and S₂ = 5, so Sm = 15. The formula also gives 2(20) − 25 = 15.
• Why there is a kink: the two firms have different shut-down prices (10 and 15). At p = 15 a second firm starts producing. So the slope of market supply jumps from 1 to 2, and the curve gets flatter (quantity responds more to price) above p = 15.
• Graph (Fig 4.13): at price p₃, firm 1 supplies q₃ and firm 2 supplies q₄. So market supply is q₅ = q₃ + q₄.

7. Drill answers (NCERT exercises)

• Exercise 22: two firms with identical schedules. Market supply = 0, 0, 0, 2, 4, 6, 8.
• Exercise 23: firm 2 starts producing at p = 4. Market supply = 0, 0, 0, 1, 2.5, 4, 5.5, 7, 8.5 kg. This is another kinked-supply case.
• Exercise 24: three identical firms, so market supply = 3 × firm supply = 0, 0, 6, 12, 18, 24, 30, 36, 42.

8. Limits and exceptions (beyond NCERT)

• Fixed-supply goods (land, antiques, stadium seats): quantity cannot rise even if price rises. The supply curve is vertical (perfectly inelastic).
• Perishables (tomatoes, fish): these cannot be stored, so at the end of the day sellers dump stock at almost any price. The Class 9 question on why tomato prices fall by evening is based on this.
• Indian scale of the problem: the Ministry of Food Processing Industries (MoFPI) had NABCONS (NABARD Consultancy Services) study post-harvest losses in 2022. It covered 54 commodities, 15 agro-climatic zones and 292 districts [8].

• Losses in fruits and vegetables were mainly due to inefficient harvesting, handling, storage and transportation [8].

• Speculative holding back: if sellers expect prices to rise further, they may supply less now even when the current price rises. This goes against the law of supply. In the model it is a leftward shift caused by price expectations, which is one of the supply factors [2].

• Policy response: the Price Stabilisation Fund (PSF) keeps a strategic buffer of commodities such as onion, potato and pulses. Stock is released in a calibrated way to moderate price volatility and discourage hoarding and speculation [7].
• Onion buffer: 2.08 lakh tonnes (LMT) of Rabi-2021 onion was procured in 2021-22, and the target for 2022-23 was set at 2.50 LMT [5]. In 2025, 3 lakh tonnes was procured, with calibrated releases expected from September 2025 [6].

• Releases are aimed at cities or states where prices are rising, and at source mandis (wholesale markets) to increase supply there [5]. In supply-curve terms, the government adds its own supply and shifts market supply right in the lean season.

• Operation Greens: a scheme to smooth the supply of perishables.

• It was announced in Union Budget 2018-19 with an outlay of ₹500 crore and launched by MoFPI in November 2018 to stabilise the supply of Tomato, Onion, Potato (TOP) and control their price volatility [3][4].
• Short-term tools: 50% subsidy on transport and storage. Long-term tools: grants of 35–70% of project cost, up to ₹50 crore per project, for value-addition projects in production clusters [3][4].
• The MIEWS portal (Market Intelligence and Early Warning System) tracks TOP prices and arrivals and sends alerts when intervention is needed [9].

• Scope was widened from TOP to 22 perishable crops (including mango, banana, apple) for the 2021-26 cycle [4].

• Backward-bending labour supply: labour supply is the hours people are willing to work at each wage. Beyond a high wage, workers may choose more leisure and supply fewer hours, so the curve bends back. See market-equilibrium-price-controls.

Prelims Hooks

• Law of supply: price and quantity supplied are directly related, other things being equal. The supply curve slopes upward.
• In a supply graph, price is on the Y-axis and quantity is on the X-axis [2].
• Market supply = horizontal summation of individual supply curves. Add quantities at the same price, not prices.
• A change in the good's own price causes a movement along the curve. A change in technology, input cost, number of sellers, expectations or related-goods prices causes a shift [2].
• With n identical firms, market supply = n × firm supply (NCERT Ex. 24: 3 firms → 0, 0, 6, 12 … 42).
• Kinked market supply arises because firms have different shut-down prices. For S₁ = p − 10 (p ≥ 10) and S₂ = p − 15 (p ≥ 15), market supply for p ≥ 15 = 2p − 25.
• Trap: a mid-season fall in mango prices is a rightward shift in supply. It is not the law of supply "failing".
• Vertical supply curve: land, antiques, stadium seats (fixed supply).
• Operation Greens: MoFPI, Budget 2018-19, ₹500 crore, TOP crops, expanded to 22 perishables (2021-26) [3][4]. MIEWS is its price-monitoring portal [9].
• The Price Stabilisation Fund maintains buffers of onion, potato and pulses for calibrated release [7].

Mains Points

• Supply shocks in perishables and food inflation (GS-III):
• TOP crops have seasonal gluts and lean-season shortages, so prices swing sharply.
• Poor cold storage and high post-harvest losses (NABCONS 2022 study) mean supply cannot be spread over the year [8].

• Operation Greens (transport and storage subsidy, value-addition grants) tries to move supply from glut months to lean months [3][4].

• Buffer stocks as a supply tool:

• PSF buffer releases (2.08 LMT onion in 2021-22; 3 LT in 2025) shift supply right when prices spike [5][6].

• Trade-off: holding the buffer costs money, and the stock can rot. Releases can also depress farmers' prices if timed badly.

• Expectations and hoarding:

• When sellers expect higher prices, they hold back supply, which breaks the simple law of supply.

• This is why stock limits under the Essential Commodities Act and calibrated buffer releases are used to discourage speculation [7].

• Number of firms and market supply:

• More firms push the market supply curve right. So policies that make entry easier (ease of doing business, a single national agricultural market such as e-NAM) raise supply and help keep prices low.