## Role of Price Elasticity of Demand – Wall Street Journal

Below is a very good video from the Wall Street Journal on price elasticity of demand (PED). PED is key to understanding how companies price their products. Consumer spending has held up relatively well so far despite inflation, but experts say we’re approaching an inflection point. The WSJ explains the role ‘elasticity’ plays in a company’s decision on whether to raise prices. After the video I’ve included some notes about calculating PED and a mindmap.

Price Elasticity of Demand (PED)
This measures the relative amount by which the quantity demanded will change in response to change in the price of a particular good. The equation is:

% change in Quantity ÷ Demanded % change in Price

How is PED calculated?

Consider the following demand schedule for buses in a city centre.

Price (average fare)          Quantity of passengers per week
100c                                      1000
60c                                        1300
30c                                        2275

Suppose the current average fare was 100c, what is the PED if fares are cut to 60c?

The percentage change in QD is equal to:
• The change in demand 300 (1300-1000) divided by the original level of demand 1000. To obtain a percentage this must be multiplied by 100. The full calculation is (300 ÷ 1000) x 100 = 30%

The percentage change in price is equal to:
• The change in price 40c (100c – 60c) divided by the original price 100c. To obtain a percentage this must be multiplied by 100. The full calculation is (40 ÷ 100) x 100 = 40%

These two figures can then be inserted into the formula with 30% ÷ 40% = 0.75
Let us now consider the PED when the average fare is cut from 60c to 30c

The percentage change in QD is equal to:
• The change in demand 975 (2275-1300) divided by the original level of demand 1300. To obtain a percentage this must be multiplied by 100. The full calculation is (975 ÷ 1300) x 100 = 75%

The percentage change in price is equal to:
• The change in price 30c (60c – 30c) divided by the original price 60c. To obtain a percentage this must be multiplied by 100. The full calculation is (30 ÷ 60) x 100 = 50%

These two figures can then be inserted into the formula with 75% ÷ 50% = 1.5

Please note that the minus sign is often omitted in PED, as the price elasticity is always negative because demand curves slope downwards. The textbook displays figures as:
PED = (-) 0.2

What price elasticity of demand figures tell us.

Determinants of Elasticity of Demand

The elasticity of a product is influenced by:
• the number of substitutes available
• whether it could be described as a luxury or a basic commodity
• the proportion of the purchaser’s income it represents
• the durability of the product.

Usefulness of Price Elasticity of Demand

The usefulness of price elasticity for producers. Firms can use price elasticity of demand (PED) estimates to predict:

1. The effect of a change in price on the total revenue & expenditure on a product.

The relationship between elasticity and total revenue.

Elastic         Inelastic            Unitary
Price ↑           TR↓                TR↑                      No Change
Price ↓           TR↑                TR↓                      No Change

2. The likely price volatility in a market following unexpected changes in supply.

3. The effect of a change in GST (indirect tax) on price and quantity demanded and also whether the business is able to pass on some or all of the tax onto the consumer.

4. Information on the price elasticity of demand can be used by a business as part of a policy of price discrimination – off-peak and peak travel in major cities. Before 9am – inelastic demand curve – after 9am elastic demand curve.

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## War on drugs – focus on supply or demand?

I have blogged on this before but find it very useful in teaching Price Elasticity of Demand (see also mindmap at end of post) with my class. Tom Wainwright’s book “Narconomics: How to Run a Drug Cartel”is a useful source for discussion and he also wrote an article for the Wall Street Journal on “How economists would wage the war on drugs”. Essentially, the war on drugs is being lost. Badly. As Wainwright notes:

The number of people using cannabis and cocaine has risen by half since 1998, while the number taking heroin and other opiates has tripled. Illegal drugs are now a \$300 billion world-wide business, and the diplomats of the U.N. aren’t any closer to finding a way to stamp them out.

This failure has a simple reason: Governments continue to treat the drug problem as a battle to be fought, not a market to be tamed. The cartels that run the narcotics business are monstrous, but they face the same dilemmas as ordinary firms-and have the same weaknesses.

El Salvador – a leader of one of the country’s two gangs has a human resource issue with high turnover of employees.

Mexico – the Zetas cartel franchises its brand like McDonalds which in turn has led to arguments over territory.

Rich countries – street corner dealers are struggle to compete on price and quality with the ‘dark web’. It is a similar scenario with Amazon.

To combat the drug trade governments have focused on restricting the supply. Each year acres of coca plants and manufacturing activities are destroyed but the price has remains around \$150-\$200 per pure gram for the past 20 years. How have the cartels managed to keep this price?

However, supply of drugs might not even be appreciably reduced when drug crops are targeted. Wainwright points out that:

1. Drug cartels are a monopsony – they are a single buyer of Andean coca leaves, so they have market power over the price of leaves (i.e. the cartels have the ability to strongly influence the market price of coca leaves). So if some crops are wiped out, the price is unlikely to rise because of the cartels’ market power.
2. The price of cocaine is so much higher than the crop input costs that even a large increase in crop prices would have little effect on the market price of cocaine (i.e. even a big increase in the price of coca leaves would lead to only a small shift in the supply curve for cocaine).

Also because of its addictive nature demand for drugs is relatively inelastic – the decrease in quantity demanded is less than the percentage increase in price. Therefore reduced supply and a higher price doesn’t change demand that much.

Demand-Side interventions seem to be a better option and they are also a lot cheaper. Weighing up reducing supply by destroying coca crops in remote areas against drug education in schools and you find the latter is a much more plausible option. Tom Wainwright’s explain this below in his talk to the Cato Institute below:

A dollar spent on drug education in U.S. schools cuts cocaine consumption by twice as much as spending that dollar on reducing supply in South America

Bigger loses have be inflicted on cartels with some US states making marijuana legal.

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## AS Economics – Price Elasticity of Demand

Doing some revision courses for AS students and went over Price Elasticity of Demand. Might be useful for those doing AS at the moment.

Price Elasticity of Demand (PED)
This measures the relative amount by which the quantity demanded will change in response to change in the price of a particular good. The equation is:

% change in Quantity ÷ Demanded % change in Price

How is PED calculated?

Consider the following demand schedule for buses in a city centre.

Price (average fare)          Quantity of passengers per week
100c                                      1000
60c                                        1300
30c                                        2275

Suppose the current average fare was 100c, what is the PED if fares are cut to 60c?

The percentage change in QD is equal to:
• The change in demand 300 (1300-1000) divided by the original level of demand 1000. To obtain a percentage this must be multiplied by 100. The full calculation is (300 ÷ 1000) x 100 = 30%

The percentage change in price is equal to:
• The change in price 40c (100c – 60c) divided by the original price 100c. To obtain a percentage this must be multiplied by 100. The full calculation is (40 ÷ 100) x 100 = 40%

These two figures can then be inserted into the formula with 30% ÷ 40% = 0.75
Let us now consider the PED when the average fare is cut from 60c to 30c

The percentage change in QD is equal to:
• The change in demand 975 (2275-1300) divided by the original level of demand 1300. To obtain a percentage this must be multiplied by 100. The full calculation is (975 ÷ 1300) x 100 = 75%

The percentage change in price is equal to:
• The change in price 30c (60c – 30c) divided by the original price 60c. To obtain a percentage this must be multiplied by 100. The full calculation is (30 ÷ 60) x 100 = 50%

These two figures can then be inserted into the formula with 75% ÷ 50% = 1.5

Please note that the minus sign is often omitted in PED, as the price elasticity is always negative because demand curves slope downwards. The textbook displays figures as:
PED = (-) 0.2

What price elasticity of demand figures tell us.

Determinants of Elasticity of Demand

The elasticity of a product is influenced by:
• the number of substitutes available
• whether it could be described as a luxury or a basic commodity
• the proportion of the purchaser’s income it represents
• the durability of the product.

Usefulness of Price Elasticity of Demand

The usefulness of price elasticity for producers. Firms can use price elasticity of demand (PED) estimates to predict:

1. The effect of a change in price on the total revenue & expenditure on a product.

The relationship between elasticity and total revenue.

Elastic         Inelastic            Unitary
Price ↑           TR↓                TR↑                      No Change
Price ↓           TR↑                TR↓                      No Change

2. The likely price volatility in a market following unexpected changes in supply.

3. The effect of a change in GST (indirect tax) on price and quantity demanded and also whether the business is able to pass on some or all of the tax onto the consumer.

4. Information on the price elasticity of demand can be used by a business as part of a policy of price discrimination – off-peak and peak travel in major cities. Before 9am – inelastic demand curve – after 9am elastic demand curve.

## Cobweb Theory and Price Elasticity

I have blogged on this topic before and although not in the NCEA or CIE syllabus’ I find it useful theory to mention when doing supply, demand and elasticity. Agricultural markets are particularly vulnerable to price fluctuations. many agricultural products have inelastic demand and inelastic supply. This means that any change in demand or supply has more of an impact on price than on quantity. Price fluctuations can also arise due to the time lag between planning agricultural production and selling the produce. The cobweb theory (so-called because of the appearance of the diagram) suggests that price can fluctuate around the equilibrium for some time, or even move away from the equilibrium. Dairy farmers base their production decisions on the price prevailing in the previous time period.

The supply of dairy products in New Zealand fits this assumption – farmers make their production decisions today, but the dairy cooperatives (Fonterra, Westland, etc.) don’t make a final decision on the price farmers will receive until close to the end of the season.

Cobweb scenarios:
Convergent
At the equilibrium point, if the demand curve is more elastic than the supply curve, we get the price volatility falling, and the price will converge on the equilibrium. For example:

• Adverse weather conditions means their is a poor crop – Qt
• The excess demand causes the price to rise – Pt
• Because of the higher price famers plant more crops and therefore greater supply – Qt+1
• With supply so high prices drop to meet demand – Pt+1
• Lower prices mean that famers supply less to the following year – Qt+2
• This results in higher prices again – Pt+2
• Because of the higher price famers plant more crops and therefore greater supply – Qt+3 etc.
• This process continues until you get to an equilibrium as the PED is greater than the PES – supply curve is steeper than the demand curve.

Continuous
This is occurs where there is a continuous fluctuation between two equilibriums – Pt and Pt+1. The PED and the PES are equal to each other.
Divergent
Prices will diverge from the equilibrium when the PES greater than the PED at the equilibrium point – i.e.the demand curve is steeper than the supply – price changes could increase and the market becomes more changeable.

Even though these three diagrams show very different results they are dependent on the PES and the PED of the market.