What is Supply and Demand?
Supply and demand is the economic law that explains how prices are determined in markets — when demand rises or supply falls, prices go up, and vice versa.
Supply and demand states that price adjusts until the quantity supplied equals the quantity demanded at market equilibrium. Higher demand or lower supply pushes price up.
Step-by-step worked examples
Coffee prices rise when frost damages the coffee crop (reducing supply). Explain why using supply and demand.
Frost → supply of coffee decreases With same demand but less supply, shortage forms Price rises until demand falls to match the lower supply New equilibrium: lower quantity, higher price
During a pandemic, remote work tools like Zoom see surging demand. What happens to price and quantity?
Pandemic → demand for remote tools increases Supply cannot immediately increase Shortage forms (demand > supply) Price rises, quantity increases, until new equilibrium New equilibrium: higher price and higher quantity
A farmer grows tomatoes. If supermarkets suddenly want fewer tomatoes (demand falls), what happens?
Supermarket demand decreases (buyers want fewer) Supply stays the same initially (tomatoes already grown) Surplus forms (supply > demand) Price falls until buyers want more New equilibrium: lower price and lower quantity
Flashcards
Quick quiz
Q1.Movie tickets cost $10 and 1000 are sold weekly. Theater doubles ticket prices to $20. What likely happens?
Q2.A new iPhone is released. Demand surges but supply is limited. What happens to price?
Q3.What causes a surplus in a market?
Q4.If farmers produce more wheat and demand stays the same, what happens?
The full card deck, worked steps and AI-tutor support for “What is Supply and Demand?” are in Notek — study by hand before your exam.
Common mistakes
Thinking supply and demand only apply to goods, not services. — Correct: Supply and demand set prices for everything: haircuts, rent, wages, concert tickets.
Confusing 'high demand' with 'high price.' — Correct: High demand alone doesn't raise price—it does only if supply can't keep up.
Assuming prices always adjust instantly to equilibrium. — Correct: Real markets have delays, hoarding, and price controls that slow adjustment.
Believing government can ignore supply and demand. — Correct: Price controls that ignore supply and demand create shortages (low price) or surpluses (high price).
FAQ
What is the law of supply and demand?
Price rises when demand exceeds supply (shortage), and price falls when supply exceeds demand (surplus). Equilibrium is reached when supply equals demand.
Why do prices go up?
Demand increases, supply decreases, or both. When buyers want more than available, sellers raise prices to ration the good.
What causes shortages and surpluses?
Shortage: demand > supply (price too low). Surplus: supply > demand (price too high). Both signal that price needs to change.
How does supply and demand affect real life?
Every price you pay — coffee, rent, wages, gas — reflects supply and demand. Pandemics, wars, new tech all shift these curves.