change in tastes away from snail mail is to decrease the equilibrium price. Since the two effects are in opposite

directions, unless we know the magnitudes of the two effects, the overall effect is unclear. This is not unusual.

When both curves shift, typically we can determine the overall effect on price or on quantity, but not on both.

In this case, we determined the overall effect on the equilibrium quantity, but not on the equilibrium price. In

other cases, it might be the opposite.

The next Clear It Up feature focuses on the difference between shifts of supply or demand and movements

along a curve.

CLEAR IT UP

What is the difference between shifts of demand or supply versus movements along a demand or
supply curve?
One common mistake in applying the demand and supply framework is to confuse the shift of a demand or a supply

curve with movement along a demand or supply curve. As an example, consider a problem that asks whether a
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