Last year, Joan bought 50 pounds of hamburger when her household's income was $40,000. This year, her household income was only $30,000 and Joan bought 60 pounds of hamburger. All else constant, Joan's income elasticity of demand for hamburger is

a. positive, so Joan considers hamburger to be an inferior good.

b. positive, so Joan considers hamburger to be a normal good and a necessity.

c. negative, so Joan considers hamburger to be an inferior good.

d. negative, so Joan considers hamburger to be a normal good but not a necessity.

a. positive, so Joan considers hamburger to be an inferior good.

Explanation:

Income elasticity is a microeconomic concept that aims to measure the sensitivity of demand in the face of income changes. To calculate the Income elasticity, a formula is used that divides the observed percentage change in quantity (Q) by the percentage change in price income (P) : Elasticity = ▲ Q / ▲ P

The percentage change in quantity (▲ Q) and the percentage change in price (▲ P) are calculated by the difference in quantity / price in the two periods divided by the quantity / price of the first period.

▲ Q = (60 - 50/60) = 0,16

▲ Q = (40.000 - 30.000/40.000) = 0,25

Elasticity = ▲ Q / ▲ P = 0,16/0,25 = 0,64

Therefore, the elasticity is positive.

This good is considered inferior, because according to microeconomic theory, inferior goods are those whose demand increases when consumer income decreases. This is the opposite of the normal good, which has its demand increased when income increases.