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薄利多銷 ?. Total expenditure (Total sales) = P × Q Total Cost = direct cost + indirect cost Profit = Total sales - Total Cost 薄利 implies lowering price 多銷 means more sales. 嚴刑重罰 Or 寓禁於徵 ?. What do you think?
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薄利多銷? • Total expenditure (Total sales) = P × Q • Total Cost = direct cost + indirect cost • Profit = Total sales - Total Cost • 薄利 implies lowering price • 多銷 means moresales NCCU 2006
嚴刑重罰 Or 寓禁於徵 ? • What do you think? • Could reducing the supply of illegal drugs cause an increase in drug-related burglaries? NCCU 2006
Total Expenditure = P x Q S $250 = $50 x 50 S’ $320 = $80 x 40 S’ 80 S 50 D 40 50 The Effect of Extra CustomPatrols on the Market for Illicit Drugs P($/ounce) Q(1,000s of ounces/day) NCCU 2006
Using Price Elasticity of Demand: The War on Drugs • Every year U.S. Government spends about $20 billion on efforts to restrict the supply of drugs • Figure (a) • Market for heroin without government intervention • Figure (b) • Result of government efforts to restrict supply (current policy) • Figure (c) • Results of an effective policy of reducing demand NCCU 2006
(a) (b) (c) Price Price Price S 2 per per per Unit Unit Unit B S S S 1 1 1 P 2 A A A P P P 1 1 1 C P 3 D D D 1 1 1 D 2 Q Q Q Q Q 1 3 1 2 1 Quantity Quantity Quantity 3 conditions in the War on Drugs NCCU 2006
Price Elasticity of Demand • Elasticity • A measure of the extent to which quantity demanded and quantity supplied respond to variations in price, income, and other factors. • 中文定義: 對價格之敏感度 NCCU 2006
Price Elasticity of Demand • Defined • Generally • A measure of the responsiveness of the quantity demanded of a good to a change in the price of that good • Formally • The percentage change in the quantity demanded that results from a 1 percent change in its price NCCU 2006
Price Elasticity of Demand • Measuring Price Elasticity of Demand NCCU 2006
Price Elasticity of Demand • Assume • The price of pork falls by 2% and the quantity demanded increases by 6% • Then the price elasticity of demand for pork is NCCU 2006
Price Elasticity of Demand • Measuring Price Elasticity of Demand • Observations • Price elasticity of demand will always be negative (i.e., an inverse relationship between price and quantity) • For convenience we drop the negative sign NCCU 2006
> 1: elastic When is < 1: inelastic = 1: unit elastic Price Elasticity of Demand • Measuring Price Elasticity of Demand NCCU 2006
Unit elastic Inelastic Elastic Elastic and Inelastic Demand Price elasticity of demand 0 1 2 3 NCCU 2006
Price Elasticity of Demand • What is the elasticity of demand for pizza? • Originally • Price = $1/slice • Quantity demanded = 400 slices/day • New • Price = $0.97/slice • Quantity demanded = 404 slices/day, then NCCU 2006
Price Elasticity of Demand • What is the elasticity of season ski passes? • Originally • Price = $400 • Quantity demanded = 10,000 passes/year • New • Price = $380 • Quantity demanded = 12,000 passes/year, then NCCU 2006
Determinants of Price Elasticity of Demand • Substitution Possibilities • Budget Share • Time NCCU 2006
Price Elasticity (in US) Estimates for Selected Products Good or service Price elasticity Green peas 2.80 Restaurant meals 1.63 Automobiles 1.35 Electricity / gasoline? 1.20 Beer 1.19 Movies 0.87 Air travel (foreign) 0.77 Shoes 0.70 Coffee 0.25 Theater, opera 0.18 WHY? NCCU 2006
Question? • Why is the price elasticity of demand more than 14 times larger for green peas than for theater and opera performances? NCCU 2006
Discussion • Economic Naturalist • Will higher taxes on cigarettes curb teenage smoking? • Why was the luxury tax on yachts such a disaster? NCCU 2006
A Graphical Interpretationof Price Elasticity • For small changes in price Where Q is the original quantity and P is the original price NCCU 2006
A Graphical Interpretationof Price Elasticity • Example • Originally • Price (P) = $100 • Quantity (Q) = 20 • New • Price (P) = $105 • Quantity (Q) = 15 NCCU 2006
A P P P - P Q D Q Q + Q A Graphical Interpretation of Price Elasticity of Demand Price Quantity NCCU 2006
D A Calculating Price Elasticity of Demand 20 16 12 Price 8 4 1 2 3 4 5 Quantity NCCU 2006
D Question What is the price elasticity of demand when P = $4? A Calculating Price Elasticity of Demand 20 16 12 Price 8 4 1 2 3 4 5 Quantity NCCU 2006
12 D1 6 4 D2 4 6 12 Price Elasticity and the Steepness of the Demand Curve What is the price elasticity of demand when P = $4? Price Quantity NCCU 2006
For D2when P = $1 12 D1 6 4 D2 1 4 6 10 12 Price Elasticity and the Steepness of the Demand Curve Price Quantity NCCU 2006
Observation If two demand curves have a point in common, the steeper curve must be less elastic with respect to price at that point 12 D1 6 Price 4 D2 1 4 6 10 12 Quantity Price Elasticity and the Steepness of the Demand Curve NCCU 2006
Observation Price elasticity varies at every point along a straight-line demand curve a a/2 b/2 b Price Elasticity Regions along a Straight-Line Demand Curve Price Quantity NCCU 2006
Price Quantity Perfectly Elastic Demand Curve NCCU 2006
Price Quantity Perfectly Inelastic Demand Curve NCCU 2006
What is the price elasticity of demand? 6 A 4 P Q B 3 4 6 12 Two Points on a Demand Curve Price 0 Quantity NCCU 2006
A Graphical Interpretationof Price Elasticity • The Midpoint Formula and NCCU 2006
6 A 4 P Q B Price 3 0 4 6 12 Quantity Two Points on a Demand Curve Then the price elasticity of demand between A and B: NCCU 2006
Elasticity and Total Expenditure • Total Expenditure = P x Q • Market demand measures the quantity (Q) at each price (P) • Total Expenditure = Total Revenue NCCU 2006
D Total Expenditure = $1,000/day A The Demand Curve for Movie Tickets 12 10 8 6 Price ($/ticket) 4 2 0 1 2 3 4 5 6 Quantity (100s of tickets/day) NCCU 2006
D Total Expenditure = $1,600/day B The Demand Curve for Movie Tickets 12 10 8 6 Price ($/ticket) 4 2 0 1 2 3 4 5 6 Quantity (100s of tickets/day) NCCU 2006
Elasticity and Total Expenditure • What do you think? • Will increasing the market price always increase total revenue? NCCU 2006
Again,薄利多銷? NCCU 2006
Total Expenditure = $1,600/day D The Demand Curve for Movie Tickets 12 10 8 6 Price ($/ticket) 4 2 0 1 2 3 4 5 6 Quantity (100s of tickets/day) NCCU 2006
Total Expenditure = $1,000/day D The Demand Curve for Movie Tickets 12 10 8 6 Price ($/ticket) 4 2 0 1 2 3 4 5 6 Quantity (100s of tickets/day) NCCU 2006
Elasticity and Total Expenditure • General Rule • A price increase will increase total revenue when the % change in P is greater than the % change in Q. NCCU 2006
12 10 8 6 Price ($/ticket) 4 2 0 1 2 3 4 5 6 Quantity (100s of tickets/day) The Demand Curve for Movie Tickets NCCU 2006
Total Expenditure as a Function of Price Price ($/ticket) Total expenditure ($/day) 12 0 10 1,000 8 1,600 6 1,800 4 1,600 2 1,000 0 0 NCCU 2006
12 1,800 1,600 10 8 1,000 6 Total expenditure ($/day) Price ($/ticket) 4 2 0 0 2 4 6 8 10 12 1 2 3 4 5 6 Price ($/ticket) Quantity (100s of tickets/day) Total Expenditure as a Function of Price Total revenue is at a maximum at the midpoint on a straight-line demand curve NCCU 2006
Elasticity and Total Expenditure • What do you think? • Should a rock band raise or lower its price to increase total revenue? • Assume NCCU 2006
Elasticity and Total Expenditure • What do you think? • Should a rock band raise or lower its price to increase total revenue? • Then • Total revenue = $20 x 5,000 = $100,000/week • If P is increased 10%, Q will decrease 30% • Total revenue = $22 x 3,500 = $77,000/week • If P is lowered 10%, Q will increase 30% • Total revenue = $18 x 6,500 = $177,000/week NCCU 2006
Elasticity and Total Expenditure • Rule • When price elasticity is greater than 1, changes in price and changes in total expenditures always move in opposite directions. • When price elasticity is less than 1, changes in price and changes in total expenditures always move in the same direction. NCCU 2006
Elasticity and Total Expenditure • Cross-Price Elasticity of Demand • The percentage by which quantity demanded of the first good changes in response to a 1 percent change in the price of the second good NCCU 2006
Elasticity and Total Expenditure • Cross-Price Elasticity of Demand • Substitute Goods • When the cross-price elasticity of demand is positive • Complement Goods • When the cross-price elasticity of demand is negative NCCU 2006
Elasticity and Total Expenditure • Income Elasticity of Demand • The percentage by which quantity demanded changes in response to a 1 percent change in income NCCU 2006