Elasticity of demand

• The law of demand tells us that when price goes up, quantity demanded goes down and viceversa.

  • But how much does quantity demanded change when price changes?

• A demand curve is said to be elastic when an increase in price redices que quantity demanded a lot.

  • When the same increase in price reduces quantity demanded just a little, then the demand curve is inelastic.

• Elasticity is a measure of how responsive quantity demanded is to a change in the price.

• Elasicity is not the same as slope

• Flatter is more elastic

• Factors that determine elasticity:

  • availability of substitutes: this is the fundamental determinant. the more substitutes the more elastic

    • for goods with many substitutes, switing brands when price change is easy, so demand is elastic

  • time horizon: immediately following a price increase, consumers may not be able to alter their consumption patterns, making demand inelastic

    • over time, however, consumers can adjust their behavior by finding substitutes

    • the longer the time horizon, the more ability to adjust

  • category of product: the broader the classification, the more likely they are able to find a substitute, making it inelastic

  • necessities vs luxiries: for necessities, consumers do not change quantity demamnded much when the price changes.

  • purchase size, relative to the consumer's budget: consumers are less concerned about price changes when the good feels cheap, making demand inelastic. they might not even notice if it goes up.

Calculating elasticity of demand

• Elasticity of demand: percentage change in quantity demanded divided by the percentage change in price.

• Ed < 1, inelastic

• Ed > 1, elastic

• Ed = 1, unit elastic

• Midpoint formula:

  

• A firm's revenues are equal to price times quantity sold

  • revenue = price * quantity sold

Elasticity of supply

• Elasticity of supply: how responsive the quantity supplied is to a change in price

• determinants of elasticity of supply

  • change in per unit costs with increased production: this is the main determinant if increased production requires higher csots, then the supply curve will be inelastic

  • time horizon: immediately following a price increase, producers can expand output only using their current capacity, making supply inelastic

  • share of market for inputs: supply is elastic when the industry is a small demander in its input markets because supply can be expanded without causing a big increase in the demand for the industry's inputs.

    • example: we can double the supply of toothpicks without making a much bigger demand for wood

  • geographic scope: the narrower the scope of the market, the more elasstic its supply

• we use the midpoint formula to calculate it too.