SUPPLY AND DEMAND CHAPTER 2 YOU ARE HERE DEFINITIONS • Supply and Demand: the name of the most important model in all economics • Price: the amount of money that must be paid for a unit of output • Market: any mechanism by which buyers and sellers exchange goods or services • Output: the good or service and/or the amount of it sold DEFINITIONS (CONTINUED) • Consumers: those people in a market who are wanting to exchange money for goods or services • Producers: those people in a market who are wanting to exchange goods or services for money • Equilibrium Price: the price at which no consumers wish they could have purchased more goods at that price; no producers wish that they could have sold more • Equilibrium Quantity: the amount of output exchanged at the equilibrium price QUANTITY DEMANDED AND QUANTITY SUPPLIED • Quantity demanded: how much consumers are willing and able to buy at a particular price during a particular period of time • Quantity supplied: how much firms are willing and able to sell at a particular price during a particular period of time CETERIS PARIBUS • As I talked about before economists use models to focus on what is most important • Models typically hold other variables constant to examine the effect of other variables. • For example in looking at the supply and demand for peanut butter we typically hold the price of jelly constant • We sometimes use the Latin phrase ceteris paribus which means “holding other things equal” to identify this case. DEMAND AND SUPPLY • Demand is the relationship between price and quantity demanded, ceteris paribus. • Supply is the relationship between price and quantity supplied, ceteris paribus. FIGURING OUT THE DEMAND CURVE • There are really two different parts to it which are similar • One is the “extensive margin” that is who buys the good • The second is the “intensive margin” or how much of the good each person buys • Guell focuses on the intensive margin, but I want to start with the extensive as I think it is easier to think about EXTENSIVE MARGIN • Think about something like an ipad where there is really no reason to buy more than one • Suppose there are 5 people in the economy and this is what they are willing to pay: Name WTP Jim $200 Jackie $400 Bill $600 Sally $800 Lisa $1000 DEMAND CURVE So what does demand look like: • • • • • • At $1200 I sell no ipads At $1000 I sell to Lisa only 1400 At $800 I sell 2 1200 At $600 I sell 3 At $400 I sell 4 1000 P And at $200 I sell5 r 800 i 600 c e 400 200 0 0 2 ipads 4 6 INTENSIVE DEMAND • Now suppose it is just one worker say me • I like to go to basketball games (either pro or college) • Suppose the seats are all the same, how many games would I go to? • • • • • • At $200 per seat I would probably go to a game At $50 per seat I would probably go to like 4 games a year At $25 I would go to like 15 At $5 I would go to like 20 At $0 I would go to like 20 Thus demand slopes down for me-the larger the price the fewer games I would go to • Demand in the economy picks up both the intensive and extensive margin THE LAW OF DEMAND The relationship between price and quantity demanded is a negative or inverse one. This occurs both on the extensive and intensive margin There are 3 reasons to expect it on the intensive margin The Substitution Effect • moves people toward the good that is now cheaper or away from the good that is now more expensive • If the price of Mobil gas goes up I buy more Amoco The Real Balances Effect • When a price increases it decreases your buying power causing you to buy less. • If I live in New York and am spending almost all of my money on rent, if rent doubles I have to move into cheaper place because I can’t afford my current place any more The Law of Diminishing Marginal Utility • The amount of additional happiness that you get from an additional unit of consumption falls with each additional unit. • This is what was really going on with my basketball tickets-I like going but I get tired of it if I go to two many games • Pretty much any good we can think of has this characteristic Put it all together and we are pretty confident that demand curves slope down p P q Q DETERMINANTS OF DEMAND • Taste • Income • Normal Goods • Inferior Goods • Price of Other Goods • Complement • Substitute • Population of Potential Buyers • Expected Price • Excise Taxes • Subsidies MOVEMENTS IN THE DEMAND CURVE Determinant Result of an Result of a increase in the decrease in the determinant determinant Taste D shifts right D shifts left Income-Normal Good D shifts right D shifts left Income-Inferior Good D shifts left D shifts right Price of Other Goods-Complement D shifts left D shifts right Price of Other Goods-Substitute D shifts right D shifts left Population of Potential Buyers D shifts right D shifts left Expected Future Price D shifts right D shifts left Excise Taxes D shifts left D shifts right Subsidies D shifts right D shifts left Example: Demand for Eating Out When Income Falls p P q2 q1 At a given price people eat out less Times Eating Out Example: Demand for ketchup when the price of beef falls p P q1 q2 Ketchup At a given price the People want more Ketchup A PITFALL: CONFUSING MOVEMENT ALONG VS. SHIFTS IN DEMAND • Price changes cause movements along a demand curve. • Other factors will cause shifts in demand. • These are not the same • The “Quantity Demanded” can change either because the price change or because the demand curve changed Two ways that Quantity Demanded can Increase: P Q SUPPLY • Supply is more complicated and harder to think about than demand (at least for me) • In demand for an ipad a person buys an ipad and brings it home • In supply for an ipad you have to design it, buy all the components, build it, ship it, sell it in the store • The Law of Supply is the statement that there is a positive relationship between price and quantity supplied. • If I am trying to sell something, the higher is the price the more I will want to sell WHY DOES THE LAW OF SUPPLY MAKE SENSE? • Because of Increasing Marginal Costs firms require higher prices to produce more output. • Because many firms produce more than one good, an increase in the price of good A makes it (at the margin) more profitable so resources are diverted from good B to produce more of good A (think about the PPF) THE SUPPLY SCHEDULE Price $0.00 $0.50 $1.00 $1.50 $2.00 $2.50 Individual Qs 0 0 1,000 2,000 3,000 4,000 QS for 10 firms 0 0 10,000 20,000 30,000 40,000 THE SUPPLY CURVE P Supply $2.50 $2.00 $1.50 $1.00 $0.50 0 0 10 20 30 40 50 Q (in thousands) MOVEMENTS IN THE SUPPLY CURVE Determinant Result of an increase in the determinant Result of a decrease in the determinant Price of Inputs S shifts left S shifts right Technology S shifts right S shifts left Price of Other Potential Outputs S shifts left S shifts right Number of Sellers S shifts right S shifts left Expected Future Price S shifts left S shifts right Excise Taxes S shifts left S shifts right Subsidies S shifts right S shifts left NUMBER OF SELLERS GOES UP P $2.50 At a given price supply will increase $2.00 $1.50 $1.00 $0.50 0 0 10 20 30 40 50 Q (in thousands) PRICE OF AN INPUT GOES UP P $2.50 $2.00 At a given price supply $1.50 will decrease $1.00 $0.50 0 0 10 20 30 40 50 Q (in thousands) MARKET EQUILIBRIUM • A competitive market is in equilibrium when price has moved to a level at which quantity demand equals quantity supplied of that good. • Competitive markets have many buyers and sellers and none is large enough to individually affect the price. • Why do markets reach an equilibrium? • If prices are too high, there is excess supply (a surplus) and firms will lower prices. • If prices are too low, there is excess demand (a shortage) and firms will raise prices. A COMBINED SUPPLY AND DEMAND SCHEDULE Price QD QS $0.00 $0.50 $1.00 $1.50 $2.00 $2.50 50,000 40,000 30,000 20,000 10,000 0 0 0 10,000 20,000 30,000 40,000 Shortage Surplus 50,000 40,000 20,000 20,000 40,000 THE SUPPLY AND DEMAND MODEL $2.50 Supply P $2.00 Equilibrium $1.50 $1.00 Demand $0.50 0 0 10 20 30 40 50 Q (in thousands) WHAT IF PRICE TOO HIGH? $2.50 Supply Surplus P $2.00 $1.50 $1.00 Demand $0.50 0 0 10 20 30 40 50 Q (in thousands) WHAT IF PRICE TOO LOW? $2.50 Supply P $2.00 $1.50 $1.00 Shortage $0.50 Demand 0 0 10 20 30 40 50 Q (in thousands) WHAT IF PRICE OF A SUBSTITUTE INCREASES? $2.50 Supply $2.00 P $1.50 New Equilibrium Old Equilibrium $1.00 New Demand Demand $0.50 0 0 10 20 30 40 50 Q/t Demand Increases Prices Quantities Increase Increase WHAT IF GOOD GETS BAD REVIEWS? $2.50 Supply $2.00 P $1.50 Old Equilibrium $1.00 New Equilibrium $0.50 Demand New Demand 0 0 10 20 30 40 50 Q/t Prices Quantities Demand Increases Increase Increase Demand Decreases Decrease Decrease TECHNOLOGY IMPROVES $2.50 P $2.00 Supply New Supply $1.50 Old Equilibrium $1.00 New Equilibrium $0.50 Demand 0 0 10 20 30 40 50 Q/t Prices Quantities Demand Increases Increase Increase Demand Decreases Decrease Decrease Supply Increases Fall Increases AN INCREASE IN COST OF AN INPUT New Supply $2.50 P $2.00 Supply New Equilibrium $1.50 Old Equilibrium $1.00 $0.50 Demand 0 0 10 20 30 40 50 Q/t Prices Quantities Demand Increases Increase Increase Demand Decreases Decrease Decrease Supply Increases Decrease Increase Supply Falls Decrease Increase WHY THE NEW EQUILIBRIUM? • If there is a change in supply or demand then without a change in the price of the good, there will be a shortage or a surplus. • Suppose the cost of an input increased-firms would no longer be willing to sell at the same price • They raise prices • As a result consumers purchase less AN INCREASE IN COST OF AN INPUT New Supply $2.50 P $2.00 Supply As a result of the shortage, employers can raise prices to new equilibrium where shortage goes away $1.50 shortage $1.00 $0.50 Demand 0 0 10 20 30 40 50 Q/t