Question

Difficulty: HardConsumer Equilibrium under Ordinal Utility

A consumer allocates a fixed income between Good XX and Good YY. At their current consumption combination, the Marginal Rate of Substitution of XX for YY (MRSxyMRS_{xy}) is 33, while the market price of Good XX (PxP_x) is 150\text{₦}150 and the market price of Good YY (PyP_y) is 30\text{₦}30. Assuming strictly convex indifference curves, what adjustment should the consumer make to attain consumer equilibrium under ordinal utility analysis?

  1. Decrease consumption of Good XX and increase consumption of Good YYAnswer
  2. B
    Increase consumption of Good XX and decrease consumption of Good YY
  3. C
    Increase consumption of both Good XX and Good YY simultaneously
  4. D
    Maintain the current consumption bundle as total utility is already maximized

Answer

The consumer should decrease consumption of Good XX and increase consumption of Good YY.
Under ordinal utility analysis, consumer equilibrium is attained where the indifference curve is tangent to the budget line, satisfying MRSxy=PxPyMRS_{xy} = \frac{P_x}{P_y}. Given Px=150P_x = \text{₦}150 and Py=30P_y = \text{₦}30, the price ratio is 55. Since the current MRSxyMRS_{xy} is 33, the marginal rate of substitution is less than the market price ratio (3<53 < 5). To increase MRSxyMRS_{xy} toward equilibrium, the consumer must decrease consumption of Good XX and increase consumption of Good YY, moving to a higher indifference curve tangency point.

Step-by-Step Solution

1
Calculate the price ratio of the two goods (Px/PyP_x / P_y).
Px/Py=15030=5P_x / P_y = \frac{150}{30} = 5.
The price ratio represents the slope of the budget line (the market rate of exchange between Good XX and Good YY).
2
Compare the Marginal Rate of Substitution (MRSxyMRS_{xy}) to the price ratio (Px/PyP_x / P_y).
MRSxy=3<Px/Py=5MRS_{xy} = 3 < P_x / P_y = 5.
Consumer equilibrium under ordinal utility requires MRSxy=PxPyMRS_{xy} = \frac{P_x}{P_y} at the point of tangency between the indifference curve and the budget line.
3
Determine the necessary change in consumption to restore equilibrium.
Since MRSxy<PxPyMRS_{xy} < \frac{P_x}{P_y}, the consumer values Good XX less than the market price demands. To raise MRSxyMRS_{xy} to 55, the consumer must reduce consumption of Good XX and increase consumption of Good YY along the budget line, relying on the principle of diminishing marginal rate of substitution.
Moving up and to the left along an indifference curve increases the slope (MRSxyMRS_{xy}) until it equals the slope of the budget line.

Key Concept

Consumer Equilibrium under Ordinal Utility (MRSxy=Px/PyMRS_{xy} = P_x / P_y)
Estimated Time:2m 0s
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