Relative Price:Â the price of one good compared to another
Ex: Hardcover books cost more than soft-covered books.
Shifts in the Budget Constraint
The budget constraint includes the consumer’s income and the prices of the two goods.
If income or prices change, the constraint shifts. An increase in income causes a parallel shift. An expansion in consumer opportunities causes a rotational shift.
21-2 Preferences: What a Consumer Wants
Representing Preferences with Indifference Curves
Indifference curve:Â a curve that shows consumption bundles that give the consumer the same level of satisfaction
Consumers will choose products and services that give them more satisfaction.
Marginal rate of substitution;Â the rate at which a consumer is willing to trade one good for another
The marginal rate of substitution depends on the number of prior instruments
Higher indifference curves are preferred to lower indifference curves.
Four Properties of Indifference Curves
Higher indifference curves are preferred to lower ones
Indifference curves slope downward
Indifference curves do not cross
Indifference curves are bowed inward
Two Extreme Examples of Indifference Curves
When goods are hard to substitute, indifference curves are very bowed.
Perfect substitutes:Â two goods with straight-line indifference curves
Perfect complements:Â two goods with right-angle indifference curves
21-3 Optimization: What a Consumer Chooses
The Consumer’s Optimal Choices
Optimum:Â where the indifference curve and the budget constraint touches
The optimum is the choice that will bring the most utility
The indifference curve is tangent to the budget constraint at the optimum.
The consumer chooses the quantities of the two goods so that the marginal rate of substitution equals the relative price.
Market prices of different goods reflect how much consumers value that good.
How Changes in Income Affect the Consumer’s Choices
Normal good:Â a good for which an increase in income raises the quantity demanded
Inferior good:Â a good for which an increase in income reduces the quantity demanded
How Changes in Prices Affect the Consumer’s Choices
When the price of a good falls, the consumer budget constraint shifts outward and changes slope.
When it increases, it shifts inwards and changes the slope.
Income and Substitution Effects
Income effect:Â the change in consumption that results when a price change moves the consumer to a higher or lower indifference curve
Substitution effect:Â the change in consumption that results when a price change moves the consumer along a given indifference curve to a point with a new marginal rate of substitution
The income effect is the change in consumption that results from the movement to a new indifference curve. The substitution effect is the change in consumption that results from moving to a new point on the same indifference curve with a different marginal rate of substitution.
Deriving the Demand Curve
The demand curve reflects consumption decisions.
A consumer’s demand curve is a summary of the optimums and decisions they can make.
21-4 Three Applications
Do All Demand Curves Slope Downward?
Law of demand:Â when the price of good rises, people buy less of it
Giffen goods:Â a good that violates the law of demand. These are inferior goods where the income effect dominates the substitution effect
How Do Wages Affect Labor Supply?
The time-allocation problem is a trade-off between leisure and consumption.
The chosen combination of consumption and leisure is called the optimum.
How Do Interest Rates Affect Household Saving?
If the substitution effect of a higher interest rate is greater than the income effect, savings increase.
If the substitution effect of a higher interest rate is greater than the substitution effect, savings decrease.