Questions: Labor Supply and Household Time Allocation

Question 1

After a significant promotion, a software engineer's hourly wage doubles. She responds by reducing her weekly hours from 45 to 35. Which explanation is correct?

• A. Her behavior is irrational — rational workers should always supply more labor when wages rise
• B. The substitution effect dominated: leisure became cheaper relative to consumption, so she chose more leisure
• C. The income effect dominated: her higher wage made her effectively wealthier, so she 'purchased' more leisure with her higher income
• D. Her reservation wage increased with the promotion, causing her to partially withdraw from the labor market

Answer: (C)

A wage increase triggers two opposing forces. The substitution effect makes leisure relatively more expensive (each hour of leisure now costs a foregone higher wage), pushing toward more work. The income effect makes the worker effectively richer per hour, increasing demand for all normal goods including leisure, pushing toward fewer hours. At high wages, the income effect often dominates — workers who already have abundant consumption income place increasing value on their time. This is the backward-bending portion of the individual labor supply curve.

Question 2

Why does aggregate labor supply typically slope upward even though individual labor supply curves can bend backward at high wages?

• A. High-income workers rationally suppress the income effect, maintaining upward-sloping individual curves
• B. Aggregate data smooths out individual variation, hiding the backward bend in the average
• C. As wages rise, workers previously below their reservation wage enter the labor market, adding new hours that outweigh hours reductions by existing high-wage workers
• D. The income effect is paradoxically stronger at the aggregate level, which reverses its sign

Answer: (C)

The key distinction is between the intensive margin (how many hours existing workers supply) and the extensive margin (whether workers enter the market at all). As wages rise, some existing high-wage workers may reduce hours (backward bend), but new workers who were previously below their reservation wage are drawn into the market. This population effect — new labor market entrants — typically dominates at the aggregate level, keeping aggregate supply upward-sloping over the policy-relevant range. This is why economists emphasize participation rate responses when analyzing minimum wage changes.

Question 3

When a wage increases, the substitution effect and income effect pull labor supply in opposite directions — the substitution effect increases hours worked while the income effect decreases them.

• T. True
• F. False

Answer: True

This bidirectional pull is what makes labor supply analysis more complex than simple commodity supply. The substitution effect treats leisure as relatively more expensive when wages rise — rational agents substitute away from it toward work. The income effect treats the wage increase as a wealth increase — since leisure is a normal good, higher income means workers want more of it, reducing hours. Which effect dominates depends on the worker's wage level, preferences, and the magnitude of the change. At low wages the substitution effect typically dominates; at high wages the income effect often wins.

Question 4

The reservation wage is the wage at which a worker earns maximum utility from employment, marking the peak of their individual labor supply curve.

• T. True
• F. False

Answer: False

The reservation wage is the minimum wage that induces a worker to enter the labor market at all — the threshold at which the utility from working just equals the utility from not working. Below this wage, the worker prefers to allocate all time to non-market activities. Above it, they participate. The reservation wage is an entry threshold, not a peak. The peak of the backward-bending labor supply curve (where income and substitution effects exactly balance) is a different concept and occurs at a higher wage level after the worker is already in the labor market.

Question 5

Why does a wage increase not unambiguously increase the number of hours a worker supplies, as a naive application of supply-and-demand logic might suggest?

Model answer: A wage increase does more than change the relative price of leisure — it also changes the worker's effective income. The standard supply-and-demand intuition captures only the substitution effect (leisure is now more expensive, so supply more labor). But the wage is also the worker's income per unit of time, so a higher wage makes the worker wealthier. Since leisure is a normal good, higher income increases demand for leisure, which means fewer hours worked. These two effects — the substitution effect pushing labor supply up and the income effect pushing it down — operate simultaneously. Which dominates determines whether the worker responds to a wage increase by working more or less.

This income-substitution decomposition is the same framework used in consumer theory, applied to the labor-leisure tradeoff. Labor supply is unusual among supply curves precisely because the same price (wage) that raises the opportunity cost of leisure also raises the income of the person making the decision. In most commodity markets, sellers don't get richer when the price of their good rises in the same way, which is why backward-bending supply curves are rare outside of labor economics.