What Is Supply and Demand?
Supply and demand is the foundational framework of economics, describing how the interaction of buyers and sellers determines prices. Demand reflects how much of a good consumers will buy at each price, generally more as prices fall, while supply reflects how much producers will offer, generally more as prices rise.
Where the two curves intersect is the equilibrium: the price at which the quantity buyers want exactly matches the quantity sellers provide. At any higher price there is a surplus that pushes prices down; at any lower price there is a shortage that pushes them up.
How It Works
Prices move when either curve shifts. Rising incomes, changing tastes, or a cheaper complement can shift demand outward, raising both price and quantity; new technology or cheaper inputs can shift supply outward, lowering prices while quantity grows.
How strongly quantity responds to price is called elasticity. Gasoline demand is inelastic, so a supply cut sends prices sharply higher, while demand for any single brand of soda is elastic, since buyers can easily switch.
Example
During the 2020-2021 pandemic, a semiconductor shortage collided with surging demand for cars, and used-vehicle prices in the U.S. jumped more than 40% in a year, a textbook case of supply shifting in while demand shifted out. When chip production recovered and demand cooled, prices fell back.
Why It Matters
Nearly every market phenomenon, from oil price spikes to housing shortages to wage growth, reduces to a supply and demand story, which makes the framework the starting point for any economic or equity analysis. Pricing power, a key trait investors prize, is essentially a claim about inelastic demand.
Financial markets themselves run on the same logic: a stock's price is where willing buyers meet willing sellers, and heavy demand for a hot IPO with limited float can send shares soaring on day one.
