5.4 Elasticity in Areas Other Than Price

Elasticity isn't just about price. The same core idea (how sensitive one variable is to changes in another) applies to income, the prices of related goods, labor markets, and financial markets. Understanding these other elasticities helps you predict how consumers, workers, and investors respond to changing conditions, and why policies like taxes and subsidies hit different groups differently.

Elasticity in Areas Other Than Price

Income and cross-price elasticity calculations

Income elasticity of demand measures how the quantity demanded of a good changes when consumer income changes.

$\text{Income Elasticity of Demand} = \frac{\text{\% change in quantity demanded}}{\text{\% change in income}}$

The sign and size of the result tell you two things at once: what kind of good it is and how strongly demand reacts to income shifts.

• Positive income elasticity → normal good (demand rises with income)
  • Greater than 1 → the good is income-elastic, meaning demand is highly sensitive to income changes. These tend to be luxury items like vacations or luxury cars.
  • Between 0 and 1 → the good is income-inelastic, meaning demand grows with income but not by much. Think staples like toilet paper or basic clothing.
• Negative income elasticity → inferior good (demand falls as income rises). When people earn more, they switch away from these goods. Instant noodles and bus rides are classic examples.

Cross-price elasticity of demand measures how the quantity demanded of one good responds to a price change in a different good.

$\text{Cross-Price Elasticity of Demand} = \frac{\text{\% change in quantity demanded of Good A}}{\text{\% change in price of Good B}}$

Again, the sign does the heavy lifting:

• Positive cross-price elasticity → the goods are substitutes. When Pepsi's price rises, demand for Coke increases. The larger the value, the more easily consumers switch between the two.
• Negative cross-price elasticity → the goods are complements. When the price of hot dogs rises, demand for hot dog buns falls. A more negative value means the goods are more tightly linked in consumption.
• A cross-price elasticity near zero means the two goods are essentially unrelated (the price of salt has little effect on demand for smartphones).

Supply elasticity in market analysis

The elasticity concept extends to the supply side in labor and financial markets.

Labor supply elasticity measures how responsive the quantity of labor supplied is to wage changes. Several factors shape it:

• Alternative job opportunities: Workers with many options respond more to wage changes, making labor supply more elastic.
• Worker mobility: If workers can easily relocate or retrain, supply is more elastic.
• Time horizon: Labor supply tends to be more elastic in the long run because workers have time to acquire new skills or move.

In practice, gig economy workers have relatively elastic labor supply since they can quickly shift hours in response to pay changes. Specialized surgeons have highly inelastic labor supply because years of training and licensing limit how fast the number of surgeons can change.

Elasticity in financial markets works the same way, just applied to borrowing and saving:

• Interest rate elasticity of demand for loans: How sensitive borrowing is to interest rate changes. Loans for discretionary purchases (a new boat) tend to be elastic, while loans for emergencies (medical expenses) tend to be inelastic since people borrow regardless of the rate.
• Interest rate elasticity of supply for savings: How sensitive saving is to interest rate changes. Savings in instruments like certificates of deposit tend to be more elastic (people shop around for the best rate), while retirement account contributions tend to be more inelastic (people save a set amount regardless).

Price elasticity of supply measures how responsive quantity supplied is to price changes. It depends on factors like spare production capacity, availability of inputs, and the time frame. A factory running at 50% capacity can ramp up output quickly (elastic), while one already maxed out cannot (inelastic).

Elasticity applications in economics

Taxation and elasticity

Tax incidence (who actually bears the burden of a tax) depends on the relative elasticities of supply and demand, not on who the government officially charges.

• When demand is relatively inelastic compared to supply, consumers bear more of the tax burden. Gasoline is a good example: people need to drive, so they absorb most of a gas tax through higher prices.
• When supply is relatively inelastic compared to demand, producers bear more of the burden. A tax on luxury goods, where demand is elastic but production inputs are specialized, pushes more of the cost onto producers.

The general rule: the more inelastic side of the market gets stuck with a larger share of the tax.

Subsidies and elasticity

Subsidy benefits are distributed by the same logic, just in reverse:

• If demand is relatively inelastic, consumers capture more of the subsidy benefit (healthcare subsidies tend to lower costs for patients).
• If supply is relatively inelastic, producers capture more of the subsidy benefit (agricultural subsidies often boost farm income more than they lower food prices).

Trade policies and elasticity

Tariffs and quotas also interact with elasticity:

• When domestic supply is elastic and domestic demand is inelastic, tariffs have a smaller effect on prices and quantities because domestic producers can ramp up production to replace imports.
• When domestic supply is inelastic and domestic demand is elastic, tariffs have a larger effect because domestic producers can't easily fill the gap, and consumers are sensitive to price increases. Sugar tariffs in the U.S. are a common example of this dynamic.

Measurement and application of elasticity

There are two main ways to calculate elasticity, and the choice matters:

• Arc elasticity calculates elasticity over a range of values (say, between two price points). It uses the midpoint formula and is more appropriate when you're dealing with large changes.
• Point elasticity measures elasticity at a single specific point on a curve. It's more precise for small changes and is what you'd use with calculus-based approaches.

Price discrimination is a direct application of differing elasticities. Firms charge higher prices to consumer groups with inelastic demand (business travelers booking last-minute flights) and lower prices to groups with elastic demand (students and leisure travelers booking in advance). The profit-maximizing strategy depends on correctly identifying which groups are more or less price-sensitive.