Equilibrium, shortages and surpluses
도입됨| English | 의미 |
|---|---|
| excess demand/ekˈses dɪˈmænd/ | 초과 수요 |
| excess supply/ekˈses səˈplaɪ/ | 초과 공급 |
A decision you can investigate
- A school stall offers reusable bottles. At a low price, buyers queue for bottles that are unavailable. At a high price, unsold bottles remain.
- Equilibrium concerns planned buying and selling, not whether everyone wants a bottle.
Build the explanation
- Equilibrium occurs where quantity demanded equals quantity supplied. Below equilibrium, excess demand 超额需求 can place upward pressure on price. Above it, excess supply 超额供给 can place downward pressure on price.
- A demand increase tends to raise equilibrium price and quantity with upward-sloping supply unchanged. A supply increase tends to lower price and raise quantity with downward-sloping demand unchanged.
Work through the evidence
- The schedule is: price 10, Qd 90, Qs 30; price 15, Qd 70, Qs 70; price 20, Qd 50, Qs 100. Equilibrium is 15 yuan and 70 bottles.
- At 10 yuan, excess demand = Qd − Qs = 90 − 30 = 60. At 20 yuan, excess supply = Qs − Qd = 100 − 50 = 50. Do not add the two quantities to find the imbalance.
What is equilibrium in the schedule?
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
At 15, both planned quantities are 70.
At 10 yuan, how large is the shortage?
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
Excess demand is 90 − 30 = 60.
An unsold surplus can encourage sellers to reduce price when prices are flexible.
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
A lower price encourages buying and discourages supply, reducing the imbalance.
Test the limits
- Adjustment depends on prices being able to change and buyers/sellers responding. A price control or a short production delay can prevent rapid clearing.
- A demand shift does not shift supply: the new equilibrium involves movement along the unchanged supply curve. If both curves shift, one effect may be ambiguous without magnitudes.
With demand unchanged, an increase in supply normally causes
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
The supply shift changes the intersection with existing demand.
Apply and explain your answer
- What imbalance occurs at 20 yuan in the bottle schedule?
- Excess supply of 50 bottles.
Match the terms to their meanings.
난이도 2/5 · 140 코인 + 오늘 첫 완료 시 소액 보너스
Each term describes a specific mechanism in this lesson.
Use the terms precisely
- excess demand: Quantity demanded exceeds quantity supplied at a particular price.
- excess supply: Quantity supplied exceeds quantity demanded at a particular price.
The schedule is: price 10, Qd 90, Qs 30; price 15, Qd 70, Qs 70; price 20, Qd 50, Qs 100. Equilibrium is 15 yuan and 70 bottles. At 10 yuan, excess demand = Qd − Qs = 90 − 30 = 60. At 20 yuan, excess supply = Qs − Qd = 100 − 50 = 50. Do not add the two quantities to find the imbalance.
Adjustment depends on prices being able to change and buyers/sellers responding. A price control or a short production delay can prevent rapid clearing. A demand shift does not shift supply: the new equilibrium involves movement along the unchanged supply curve. If both curves shift, one effect may be ambiguous without magnitudes.
Equilibrium occurs where quantity demanded equals quantity supplied. Below equilibrium, excess demand can place upward pressure on price. Above it, excess supply can place downward pressure on price.
Write from an excess of 60
- At 8 yuan, demand is 100 and supply is 40. At 12 yuan, both are 70. At 16 yuan, demand is 40 and supply is 100.
- Find the equilibrium and both imbalances. Do not add demand and supply.
At 8 yuan demand is 100 and supply is 40. At 12 yuan both are 70. At 16 yuan demand is 40 and supply is 100. What is the equilibrium, the excess demand and the excess supply?
Equilibrium is the price where the quantity demanded equals the quantity supplied. A shortage or surplus is the gap between them.
What is the excess demand at 8 yuan?
난이도 1/5 · 100 코인 + 오늘 첫 완료 시 소액 보너스
Demand 100 minus supply 40 is 60. Adding the two quantities is not the shortage. Other options — 140 (the sum of demand and supply); 70 (the equilibrium quantity).