Intermediate Microeconomics · free preview

Utility Functions and Ordinality

A utility function is a labeling of indifference curves, its levels carry no meaning beyond more is higher, monotone transformations preserve all its content, and special families, Cobb-Douglas and quasilinear, will carry most of the course's arithmetic.

1. A thermometer with no units

A thermometer with no units

2. Checking invariance

Checking invariance

3. The workhorse families

The workhorse families

4. Curves from utility, utility from curves

Curves from utility, utility from curves

5. What the numbers mean

Bundle A has utility 6 and bundle B has utility 3 under u=x1x2u = x_1 x_2. Which claims are meaningful?

6. The log transform's MRS

Which MRS does v=ln⁡x1+ln⁡x2v = \ln x_1 + \ln x_2 have, and how does it relate to the MRS of u=x1x2u = x_1 x_2?

7. Quasilinear geometry

For quasilinear utility u=v(x1)+x2u = v(x_1) + x_2, what is the geometric signature of the indifference map?

8. Choosing the friendly form

Why do economists so often work with v=aln⁡x1+bln⁡x2v = a \ln x_1 + b \ln x_2 instead of u=x1ax2bu = x_1^a x_2^b?

9. MRS of a weighted Cobb-Douglas

For u=x12x23u = x_1^2 x_2^3 at the bundle (2,3)(2, 3), compute the MRS in absolute value, and write the number.

10. A transformed level

Under u=x1x2u = x_1 x_2 the bundle (4,5)(4, 5) has utility 20. Compute the value of v=ln⁡uv = \ln u at that bundle, rounded to two decimals, and write the number.

11. What utility numbers are not

Under u of x1 x2, bundle A scores 6 and bundle B scores 3. Which claim is meaningful?

12. Which transforms are legal

Starting from u of x1 x2, which rewrite preserves every preference?

13. Quasilinear's signature

For u of v(x1) plus x2, what geometric property do the indifference curves have?

14. The weighted-log family

What convenience does v equal a ln x1 plus b ln x2 buy over its exponential parent?

15. The cubic-weighted ratio

For u of x1 times x2 cubed at the bundle (1, 3), compute the absolute MRS, and write the number.

16. MRS on the flat side

For u of x1 times x2, compute the absolute MRS at the bundle (5, 2), and write the number as a decimal.

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