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Zorluk: Çok zorConcept and Law of Demand
An economic analyst models the weekly consumer demand for Good XX using the linear demand function:
Qd=500−5PX+0.05Y−2PYQ_d = 500 - 5P_X + 0.05Y - 2P_Y
where QdQ_d is the quantity demanded of Good XX, PXP_X is the unit price of Good XX in Naira (₦\text{₦}), YY is monthly consumer income in Naira (₦\text{₦}), and PYP_Y is the unit price of related Good YY.

Initially, PX=₦20P_X = \text{₦}20, Y=₦4,000Y = \text{₦}4,000, and PY=₦50P_Y = \text{₦}50. If the price of Good XX increases to ₦30\text{₦}30 while monthly consumer income simultaneously rises to ₦6,000\text{₦}6,000 (with PYP_Y remaining unchanged at ₦50\text{₦}50), which of the following statements accurately analyzes the graphical behavior of the demand curve and the resulting net quantity demanded of Good XX?

  1. The increase in PXP_X causes an upward movement along the demand curve, contracting quantity demanded by 5050 units, while the increase in income causes a rightward shift of the entire demand curve by 100100 units, resulting in a net quantity demanded of 550550 units.Cevap
  2. B
    The increase in PXP_X shifts the demand curve to the left by 5050 units, while the increase in income shifts the demand curve to the right by 100100 units, resulting in a net leftward movement and a total quantity demanded of 450450 units.
  3. C
    Both the price increase of Good XX and the income increase cause movements along the existing demand curve, resulting in a total expansion of quantity demanded to 650650 units.
  4. D
    The increase in PXP_X causes an upward movement along the demand curve, but because Good XX and Good YY are complementary goods, the income rise shifts the demand curve leftward, reducing final quantity demanded to 400400 units.

Cevap

The increase in the price of Good X causes an upward movement along the demand curve, contracting quantity demanded by 50 units, while the increase in income causes a rightward shift of the entire demand curve by 100 units, resulting in a net quantity demanded of 550 units.
The option stating that the price increase causes an upward movement along the demand curve while the income increase causes a rightward shift of the curve is correct. By the Law of Demand, a change in the price of Good X (PXP_X) leads to a movement along the demand curve, reducing quantity demanded by 5×10=505 \times 10 = 50 units. Conversely, income (YY) is a non-price determinant; an increase in income increases demand at all price levels by 0.05×2,000=1000.05 \times 2,000 = 100 units, shifting the entire demand curve rightward. The net quantity demanded is 500−50+100=550500 - 50 + 100 = 550 units.

Adım Adım Çözüm

1
Calculate the initial quantity demanded (Qd1Q_{d1}) using the initial values.
Qd1=500−5(20)+0.05(4,000)−2(50)=500−100+200−100=500Q_{d1} = 500 - 5(20) + 0.05(4,000) - 2(50) = 500 - 100 + 200 - 100 = 500 units.
Establishing the baseline quantity demanded before any economic changes occur.
2
Analyze the impact of the change in own-price (PXP_X from ₦20\text{₦}20 to ₦30\text{₦}30).
Change in quantity demanded due to price = −5×(30−20)=−50-5 \times (30 - 20) = -50 units. Graphically, this is an upward/leftward movement along the demand curve (contraction of quantity demanded).
According to the Law of Demand, a change in the price of the commodity itself causes a movement along the demand curve, not a shift.
3
Analyze the impact of the change in income (YY from ��4,000\text{��}4,000 to ₦6,000\text{₦}6,000).
Change in demand due to income = +0.05×(6,000−4,000)=+100+0.05 \times (6,000 - 4,000) = +100 units. Graphically, because income is a non-price determinant, this shifts the entire demand curve to the right.
A change in non-price factors such as consumer income changes demand at every price level, causing a parallel shift of the curve.
4
Compute the final net quantity demanded (Qd2Q_{d2}).
Qd2=500−5(30)+0.05(6,000)−2(50)=500−150+300−100=550Q_{d2} = 500 - 5(30) + 0.05(6,000) - 2(50) = 500 - 150 + 300 - 100 = 550 units.
Combining the movement along the curve and the shift of the curve yields the net quantity demanded.

Anahtar Kavram

Distinction between movement along a demand curve (change in quantity demanded) and a shift of the demand curve (change in demand)
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Konular

Concept and Law of Demand

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