4.1 The 9/11 terrorist attacks caused the U.S. airline travel demand curve to shift left by an estimated 30% (Ito and Lee, 2005). Use a supply-anddemand diagram to show the likely effect on price and quantity (assuming that the market is competitive).

Indicate the magnitude of the likely equilibrium price and quantity effects—for example, would you expect equilibrium quantity to change by about 30%? Show how the answer depends on the shape and location of the supply and demand curves.