经济学原理英文ppt课件.ppt

The Market Forces of Supply and demandnA competitive market is a market in which there are many buyers and sellers so that each has a negligible impact on the market price.1What Is Competition?nCompetition: Perfect and Otherwise qPerfect CompetitionnProducts are the samenNumerous buyers and sellers so that each has no influence over pricenBuyers and Sellers are price takersqMonopolynOne seller, and seller controls price2What Is Competition?nCompetition: Perfect and Otherwise qOligopolynFew sellersnNot always aggressive competitionqMonopolistic CompetitionnMany sellersnSlightly differentiated productsnEach seller may set price for its own product3DEMANDnQuantity demanded is the amount of a good that buyers are willing and able to purchase.nLaw of DemandqThe law of demand states that, other things equal, the quantity demanded of a good falls when the price of the good rises. 4The Demand Curve: The Relationship between Price and Quantity DemandednDemand Schedule qThe demand schedule is a table that shows the relationship between the price of the good and the quantity demanded. 5Catherine’s Demand Schedule6The Demand Curve: The Relationship between Price and Quantity DemandednDemand Curve qThe demand curve is a graph of the relationship between the price of a good and the quantity demanded. 7Figure 1 Catherine’s Demand Schedule and Demand CurvePrice ofIce-Cream Cone02.502.001.501.000.50123456789 10 11Quantity ofIce-Cream Cones$3.00121. A decrease in price ...2. ... increases quantity of cones demanded.8Market Demand versus Individual DemandnMarket demand refers to the sum of all individual demands for a particular good or service.nGraphically, individual demand curves are summed horizontally to obtain the market demand curve.9The Market Demand CurvePrice of Ice-Cream ConePrice of Ice-Cream ConePrice of Ice-Cream Cone2.002.002.004371.001.001.008513Quantity of Ice-Cream ConesQuantity of Ice-Cream ConesQuantity of Ice-Cream ConesCatherine’s DemandNicholas’s DemandMarket Demand+=The market demand curve is the horizontal sum of the individual demand curves!100DPrice of Ice-Cream ConesQuantity of Ice-Cream ConesAB81.00$2.004Changes in Quantity Demanded11Shifts in the Demand CurveqConsumer incomeqPrices of related goodsqTastesqExpectationsqNumber of buyers12Figure 3 Shifts in the Demand CurvePrice ofIce-CreamConeQuantity ofIce-Cream ConesIncreasein demandDecreasein demandDemand curve, D3Demandcurve, D1Demandcurve, D2013Shifts in the Demand CurvenConsumer IncomeqAs income increases the demand for a normal good will increase.qAs income increases the demand for an inferior good will decrease.14$3.002.502.001.501.000.50213456789101211Price of Ice-Cream ConeQuantity of Ice-Cream Cones0Increasein demandAn increase in income...D1D2Consumer Income Normal Good15$3.002.502.001.501.000.50213456789101211Price of Ice-Cream ConeQuantity of Ice-Cream Cones0Decreasein demandAn increase in income...D1D2Consumer Income Inferior Good16Shifts in the Demand CurvenPrices of Related GoodsqWhen a fall in the price of one good reduces the demand for another good, the two goods are called substitutes.qWhen a fall in the price of one good increases the demand for another good, the two goods are called complements.17SUPPLYnQuantity supplied is the amount of a good that sellers are willing and able to sell. nLaw of SupplyqThe law of supply states that, other things equal, the quantity supplied of a good rises when the price of the good rises.18The Supply Curve: The Relationship between Price and Quantity SuppliednSupply ScheduleqThe supply schedule is a table that shows the relationship between the price of the good and the quantity supplied. 19Ben’s Supply Schedule20The Supply Curve: The Relationship between Price and Quantity Supplied nSupply CurveqThe supply curve is the graph of the relationship between the price of a good and the quantity supplied. 21Figure 5 Ben’s Supply Schedule and Supply CurvePrice ofIce-CreamCone02.502.001.501.0012345678910 11Quantity ofIce-Cream Cones$3.00120.501. Anincrease in price ...2. ... increases quantity of cones supplied.22Market Supply versus Individual SupplynMarket supply refers to the sum of all individual supplies for all sellers of a particular good or service.nGraphically, individual supply curves are summed horizontally to obtain the market supply curve.23Shifts in the Supply CurvenInput pricesnTechnologynExpectations nNumber of sellers241 5Price of Ice-Cream ConeQuantity of Ice-Cream Cones0S 1.00AC$3.00A rise in the price of ice cream cones results in a movement along the supply curve.Change in Quantity Supplied25Figure 7 Shifts in the Supply CurvePrice ofIce-CreamConeQuantity ofIce-Cream Cones0Increasein supplyDecreasein supplySupply curve, S3curve, SupplyS1Supplycurve, S226SUPPLY AND DEMAND TOGETHERnEquilibrium refers to a situation in which the price has reached the level where quantity supplied equals quantity demanded. 27SUPPLY AND DEMAND TOGETHERnEquilibrium PriceqThe price that balances quantity supplied and quantity demanded. qOn a graph, it is the price at which the supply and demand curves intersect.nEquilibrium QuantityqThe quantity supplied and the quantity demanded at the equilibrium price. qOn a graph it is the quantity at which the supply and demand curves intersect. 28At $2.00, the quantity demanded is equal to the quantity supplied!SUPPLY AND DEMAND TOGETHERDemand ScheduleSupply Schedule29Figure 8 The Equilibrium of Supply and DemandPrice ofIce-CreamCone0123456789101112Quantity of Ice-Cream Cones13EquilibriumquantityEquilibrium priceEquilibriumSupplyDemand$2.0030EquilibriumnSurplusqWhen price > equilibrium price, then quantity supplied > quantity demanded. nThere is excess supply or a surplus. nSuppliers will lower the price to increase sales, thereby moving toward equilibrium.31Figure 9 Markets Not in EquilibriumPrice ofIce-CreamCone0SupplyDemand(a) Excess SupplyQuantitydemandedQuantitysuppliedSurplusQuantity ofIce-CreamCones4$2.50102.00732EquilibriumnShortageqWhen price < equilibrium price, then quantity demanded > the quantity supplied. nThere is excess demand or a shortage. nSuppliers will raise the price due to too many buyers chasing too few goods, thereby moving toward equilibrium.33Figure 9 Markets Not in EquilibriumPrice ofIce-CreamCone0Quantity ofIce-CreamConesSupplyDemand(b) Excess DemandQuantitysuppliedQuantitydemanded1.5010$2.0074Shortage34EquilibriumnLaw of supply and demandqThe claim that the price of any good adjusts to bring the quantity supplied and the quantity demanded for that good into balance.35Table 3: Three Steps for Analyzing Changes in Equilibrium36Figure 10 How an Increase in Demand Affects the EquilibriumPrice ofIce-CreamCone0Quantity of Ice-Cream ConesSupplyInitialequilibriumDD3. . . . and a higherquantity sold.2. . . . resultingin a higherprice . . .1. Hot weather increasesthe demand for ice cream . . .2.007New equilibrium$2.501037Three Steps to Analyzing Changes in EquilibriumnShifts in Curves versus Movements along CurvesqA shift in the supply curve is called a change in supply.qA movement along a fixed supply curve is called a change in quantity supplied.qA shift in the demand curve is called a change in demand.qA movement along a fixed demand curve is called a change in quantity demanded.38Figure 11 How a Decrease in Supply Affects the EquilibriumPrice ofIce-CreamCone0Quantity of Ice-Cream ConesDemandNewequilibriumInitial equilibriumS1S22. . . . resultingin a higherprice of icecream . . .1. An increase in theprice of sugar reducesthe supply of ice cream. . .3. . . . and a lowerquantity sold.2.007$2.50439Table 4: What Happens to Price and Quantity When Supply or Demand Shifts?40。