Question

Difficulty: HardConsumer Equilibrium under Ordinal Utility

A consumer allocating a fixed income between Good XX and Good YY faces market prices of Px=60P_x = \text{₦}60 and Py=15P_y = \text{₦}15. At their current consumption bundle, the Marginal Rate of Substitution (MRSxyMRS_{xy}) is 33. Assuming standard indifference curves that are strictly convex to the origin, how should the consumer adjust their purchases to attain equilibrium?

  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 without modification

Answer

The consumer should decrease consumption of Good XX and increase consumption of Good YY.
In ordinal utility analysis, consumer equilibrium is reached at the point where the indifference curve is tangent to the budget line, satisfying the condition MRSxy=PxPyMRS_{xy} = \frac{P_x}{P_y}. Given Px=60P_x = \text{₦}60 and Py=15P_y = \text{₦}15, the market price ratio is 6015=4\frac{60}{15} = 4. Since the current MRSxyMRS_{xy} is 33, which is less than 44, the consumer values Good XX less than the market does at the margin. To raise MRSxyMRS_{xy} to match the market ratio of 44, the consumer must decrease consumption of Good XX and increase consumption of Good YY along the budget constraint.

Step-by-Step Solution

1
Calculate the market price ratio of Good XX to Good YY.
PxPy=6015=4.\frac{P_x}{P_y} = \frac{60}{15} = 4.
The price ratio determines the slope of the budget line.
2
Compare the current Marginal Rate of Substitution (MRSxyMRS_{xy}) to the price ratio.
MRS_{xy} = 3 < \frac{P_x}{P_y} = 4.
Equilibrium under ordinal utility requires MRSxy=PxPyMRS_{xy} = \frac{P_x}{P_y} at the point of tangency.
3
Determine the necessary adjustment to restore equilibrium along a convex indifference curve.
Reduce Good XX and increase Good YY to increase MRSxyMRS_{xy} from 33 to 44.
Due to the diminishing rate of marginal substitution, reducing consumption of XX increases MUxMU_x and increasing consumption of YY decreases MUyMU_y, which raises MRSxy=MUxMUyMRS_{xy} = \frac{MU_x}{MU_y} toward 44.

Key Concept

Consumer Equilibrium under Ordinal Utility
Estimated Time:2m 0s
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