The absolute value of the price elasticity of demand for a good increases when

The absolute value of the price elasticity of demand for a good increases when

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Intros

Lessons

  1. Cross & Income Elasticity of Demand Overview:
  2. Cross Elasticity of Demand

    • Formula for Cross Elasticity of Demand
    • Do not take the absolute value
    • Positive  →  goods are substitutes
    • Demand curve for good shifts rightward
    • Negative  →  goods are complements
    • Demand curve for good shifts leftward

  3. Cross Elasticity of Demand

    • Formula for Income Elasticity of Demand
    • Do not take the absolute value
    • Positive  →  goods are normal
    • Negative  →  goods are inferior

Examples

Lessons

  1. Calculating Cross Elasticity of Demand
    Suppose that a company decides to increase the price of juice by 20%. By doing this, they see a 15% increase in the quantity of coffee.
    1. Find the cross elasticity of demand for coffee in respect to apple juice
    2. State whether juice is a substitute or a complement.
    3. What happens to the demand curve for coffee?
  2. A company decides to increase their price of candy from $5 to $10. By doing so, the quantity of water decreases from 80 to 50, and decreases the quantity of candy from 100 to 50.
    1. Calculate the price elasticity of demand for candy using arc elasticity of demand. Is it elastic, inelastic, or unit elastic?
    2. Calculate the cross elasticity of demand for water in respect to candy. Are candies a substitute or a complement?
  3. Calculating Income Elasticity of Demand
    If Kevin's income increases from $100 to $150 a day, he increases his demand for ice cream by 10%, and decreases his demand for coffee by 20%. Calculate Kevin's income elasticity of demand for
    1. Ice cream
    2. Coffee
  4. If Patsy's income increases from $50 to $100 a week., she increases her demand for chocolate from 2 kg to 5 kg.
    1. Calculate the income elasticity demand for chocolate.
    2. Is chocolate a normal good or inferior good? Why?
    3. Is the income elastic or inelastic? Why?

What is price elasticity of demand?

Elasticity of demand is a measure used in economics to determine the sensitivity of demand of a product to price changes. In theory, this measurement can work on a wide range of products, from low priced items like pencils to more significant purchases like cars. Because of this diversity of products, elasticity of demand looks at percent changes in price rather than absolute changes; for example, a \$10 increase for a pack of pencils would be outrageous, while a \$10 increase for a new car would likely go unnoticed. Ultimately, the equation used to determine elasticity of demand can be simply thought of as: how do a price increase of X% affect the demand of product Y? A higher demand elasticity means that consumers are more responsive to changes in the price of the product.

How to determine elasticity of demand

Given that elasticity of demand calculates the relationship between change in price and change in demand, we can begin to derive the formula:

|$\frac{\text{Percent  change  in  demand}}{\text{Percent  change  in  price}}| = |\frac{∆q/q}{∆p/p}$|

This can be further simplified as:

|$\frac{∆q}{q} \cdot \frac{p}{∆p}| = |\frac{p}{q} \cdot \frac{∆q}{∆p}$|

In the above equation ∆p refers to change in price, while ∆q represents the corresponding change in the quantity of the product demanded. Absolute values are used when determining the coefficient of elasticity, because the correlation between price increase and quantity demand can be assumed to always be negative.

For small changes in price, $\frac{∆q}{∆p}$ can be approximated by the derivative $\frac{dq}{dp}$. This means that we can determine elasticity of demand, E, by substituting in the derivatives of ∆q and ∆p into the above formula.

Therefore, E = |$\frac{p}{q} \cdot \frac{dq}{dp}$|

Important values for elasticity of demand

The word “coefficient” is used to describe the values for price elasticity of demand (E). Different coefficient values have various implications for the price elasticity of demand of products:

  • E = 0: demand is perfectly inelastic, meaning that demand does not change at all when the price changes.
  • 0 < E < 1: in these cases, the % change in demand from is smaller than the percentage change in price, and the demand is inelastic.
  • E = 1: here, the % change in demand is exactly the same as the % change in price, which means that the demand is unit elastic. For example, a price increase of %10 would lead to a 10% decrease in demand.
  • E > 1: demand responds more than proportionately to a price increase, so the demand is elastic. For example if a 15% increase in the price of a product corresponds to a 45% drop in demand. In this specific case, E = 3.

The more the demand for a product decreases in relation to the change in price, the more elastic that good is considered.

Application

The demand curve for a product is given by $q = 2000−4p^2$, where p = price. What is the elasticity of the product when the price is \$10?

To solve this problem, first find $\frac{dq}{dp}$. Using the power rule, we know that $\frac{dq}{dp} = -8p$.

We plug this, as well as the price, into the equation, yielding:

$E = |\frac{10}{q} \cdot (-8)$|

To find q, we go back to our original equation.

$q = 2000−4p^2 = 2000−4(10)^2 = 1,600$

Now we have all of the components needed to calculate the price elasticity of demand at price = /$10.

$E = |\frac{10}{400} \cdot (-8)| = .2$

Considering the values of E described above, we know that the product is inelastic at p=10. Another way to think of this is that a 1% increase in price will correspond with an approximately .2% decrease in quantity demand.

Sources:

Applied Calculus 5th Edition (Hughes-Hallet, Gleason, Lock, Faith, et al.) – section 4.6

https://www.tutor2u.net/economics/reference/price-elasticity-of-demand

https://www.extension.iastate.edu/AGDM/wholefarm/pdf/c5-207.pdf

https://www.intelligenteconomist.com/price-elasticity-of-demand/

What happens when the price elasticity of demand increases?

A product with high price elasticity of demand will see demand fall sharply when prices rise. For the product with high elasticity of demand, the downward-sloping demand curve appears flatter, and for every change in price, there is a large change to the quantity demanded.

What is the absolute value of the price elasticity of demand?

Again, as with the elasticity of demand, the elasticity of supply is not followed by any units. Elasticity is a ratio of one percentage change to another percentage change—nothing more—and we read it as an absolute value. In this case, a 1% rise in price causes an increase in quantity supplied of 3.5%.

What would be the absolute value of the elasticity if demand is unit elastic?

Demand elasticity of a good with unit elastic demand is 1 (strictly speaking, elasticity equals -1 since the demand curve is downward sloping; but in most cases, elasticity is calculated as an absolute value).

What happens when the price of an inelastic good increases?

On the other hand, if the price for an inelastic good is increased and the demand does not change, the total revenue increases due to the higher price and static quantity demanded. However, price increases typically do lead to a small decrease in quantity demanded.