1. Be Careful! Change in Demand vs. Change in Quantity Demand
You can not have both an:
Increase in demand and an increase in quantity demanded or
Increase in supply and an increase in quantity supplied
The same is true for a decrease….

2. Change in Demand Increase in Demand Price Decrease in Demand D1 Qty
Curves only shift when
a determinant changes
(TIPSEN or TINE TP) D1
Qty
T-Shirts

3. Change in Quantity Demanded
Price
Ice Cream makers raise prices to 200
leads to B
$2.00
movement along existing demand curve
Called a Change in Quantity Demanded A
1.00 D 4 8
Quantity
Ice Cream

4. Test: How would you describe the change:
Price S1 P2 E2 P1 E1 D2 D1 Q1 Q2
Qty
Soda

5. Summary
ONLY when a determinant of demand or determinant of supply changes can you have a:
Increase or decrease in demand [TIPSEN]
Increase or decrease in supply [TINE & TP]
When price only changes
There is a change in quantity demanded [only price]