Interactive Graphs

How to read this graph

What changes

A determinant of demand or supply (income, tastes, input prices, expectations, number of buyers/sellers) — or a government intervention like a tax, ceiling, or floor.

Which curve

The demand curve shifts for demand-side causes; the supply curve shifts for supply-side causes. A change in the good's own price never shifts either curve — it moves you along them.

Direction

Right = increase, left = decrease. An increase in demand raises both equilibrium price and quantity; an increase in supply lowers price and raises quantity.

Why

Buyers or sellers are now willing to trade a different amount at every price, not just at one price.

Equilibrium effect

The new equilibrium is wherever the (possibly shifted) curves now intersect. A binding price ceiling or floor prevents price from reaching that point, creating a shortage or surplus instead.