## Price Elasticity of Demand Formula and Interpretation

In this first lesson on elasticities we’ll learn the definition, formula and interpretations of the price elasticity of demand (PED) coefficient.

Part 1

Part 2

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## A supply and demand paradox – Why is the Chevy Volt twice the price of the Chevy Cruze?

One of the many things I appreciate about economics is that it helps us better understand things in the world around us that without economic tools would seem like mysteries. For example, a few weeks ago I went for a hike with a friend who works for General Motors here in Switzerland. One perk of his job is that he gets to drive different GM cars around before they go on sale in Europe. He showed up to the hike in a 2012 Chevy Cruze. I commented on what a nice looking car it was and asked him how much it would sell for. He told me it would start aroun 17,000 francs here in Switzerland, and then he told me about Chevy’s new plug-in hybrid, the Chevy Volt, which would start at around 32,000 francs.

I decided to ask my IB students today to try and explain the price differences between the Chevy Volt and the Cruze using supply and demand analysis. In the video below, I offer my own economic analysis of the two cars. Watch the video and respond to the discussion questions that follow.

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## Efficiency and equilibrium in competitive markets

This week we will be wrapping up unit 1.1 from the IB Economics syllabus here in Zurich. The final topic to cover from this section of the course is the relationship between equilibrium in a competitive market and allocative efficiency. The video below explains why the most efficient result a market can hope to achieve occurs when the price and quantity are determined by the intersection of supply and demand. Any price and quantity combination other than that found at equilibrium will reduce overall efficiency and lead to a loss of societal welfare.

Discussion Questions about Efficiency:

1. “The invisible hand of the competitive market results in a more efficient allocation of resources than prices set by a government can ever hope to achieve.” Explain the economic reasoning behind this statement.
2. Why does the marginal benefit to consumers of a good decrease the greater the quantity of the good becomes available on the market? Why does the marginal cost to producers increase?
3. How do competitive market forces assure resources will be efficiently allocated towards the provision of various goods and services? In other words, if the quantity in a market is not at equilibrium, why is it likely to move towards equilibrium over time?
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## Finding equilibrium price and quantity using demand and supply equations

Now that you’ve mastered demand and supply equations, it’s time to put them together to determine the equilibrium price and quantity in a market! This less shows you how to solve for equilibrium price and quantity using linear demand and supply equations.

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## Deriving demand and supply equations from a set of data

Suppose all you knew were a couple of points from a demand or supply schedule, and you were asked to determine the equations that described the demand and supply of the product. For example, what if you knew that,

• At a price of \$5, 1,000 movie tickets would be demanded in a small town, but only 200 would be supplied, while,
• At a price of \$15, 300 movie tickets would be demanded and 1,200 would be supplied.
Could you use this information to derive the demand and supply equations for movie tickets? Could you then calculate the equilibrium price and quantity of movie tickets? Watch the video lecture that follows, and then apply what you learned to find the demand and supply equations for movie tickets using the data above. Also determine the equilibrium price and quantity of movie tickets.

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## Introduction to Linear Supply Equations

A new video on Linear Supply equations. In this lesson we’ll learn how to derive an equation representing the supply of a good using the data in a supply schedule or curve.

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## Linear Demand Equations – Shifts in Demand (changes in the ‘a’ and the ‘b’ variables)

In our 3rd lesson on linear demand equations we’ll learn how a change in a non-price determinant of demand can cause the ‘a’ variable to change and a shift inwards or outwards of the demand curve along the quantity axis.

In our final lesson on linear demand equations we’ll look at how a change in a non-price determinant of demand can cause the demand curve to pivot along the quantity axis, changing the ‘b’ variable, resulting in either an increase or a decrease in the responsiveness of consumers to price changes.

Linear Demand Equations – part 3

Linear Demand Equations – part 4

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## Introduction to Linear Demand Equations

This is an update to the 2012 version of the lesson introducing how to determine an equation for demand using price and quantity data from a demand schedule or a demand curve. In parts 2 and 3 of this lesson we’ll examine how changes in price and the non-price determinants of demand will lead to movements along a demand curve or a change in the ‘a’ and ‘b’ variables and a shift in demand.

Linear Demand Equations – Part 1

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## The Determinants of Demand (NEW 2016!)

In our third and final lesson introducing Demand we explore the non-price determinants of a good’s demand, changes to which will cause the demand for a good to increase or decrease and the demand curve to shift.

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