University:
University of Edinburgh
Course:
BUST08004 | Marketing
Academic year:

2015
Views:

427

Pages:

76
Author:

Eitminaheiq

Competitive Firms and Markets Lecture 6 Reading: Perlo¤ Chapter 8 August 2015 1 / 76 Introduction We learned last lecture what input combination a …rm will use for a given level of output. But exactly how much should a …rm produce? Depends on their cost structure, what other …rms will do and how consumers behave. 2 / 76 Introduction In this lecture, we see how the supply curve we saw on the …rst day is derived. We look in more detail how the equilibrium quantity and price is determined in a perfectly competitive market. 3 / 76 Outline Perfect Competition - A perfectly competitive …rm is a price taker and faces a horizontal demand curve. Pro…t Maximization - How much should a …rm produce to maximize pro…ts? Competition in the Short Run - What is the market equilibrium when the number of …rms in the market is …xed? Competition in the Long Run - What is the market equilibrium when …rms are free to enter and exit? 4 / 76 Perfect Competition One of the simplest market structures is perfect competition. A market is perfectly competitive if each …rm in the market is a price taker. A …rm is a price taker if it cannot alter the market price or the price at which they buy inputs. Everything the …rm needs to know is captured by the market price. 5 / 76 Perfect Competition Firms are likely to be price takers if the market has some or all of the properties Huge number of …rms Homogenous products Everybody knows everything Low transaction costs Free entry and exit Obviously these conditions are never fully met, but many markets are highly competitive. 6 / 76 Perfect Competition Large Number of Buyers and Sellers If there are enough sellers, no …rm can raise or lower the market price. An individual …rm is a tiny percent of the entire market. The …rm’s demand curve is a horizontal line at the market price. 7 / 76 Perfect Competition Identical Products Firms sell homogenous products. A good produced by …rm A is perfectly substitutable with a good produced by …rm B. A …rm cannot sell anything if it raises its price by 1P more than its competitors. An example of this would be Granny Smith apples or plain white t-shirts. 8 / 76 Perfect Competition Full Information Buyers know the prices set by all …rms. Firms cannot get away with raising their price because consumers know the prices of all …rms. 9 / 76 Perfect Competition Negligible Transaction Costs Buyers and sellers don’t have to spend much time or money to interact with each other. If this were not the case, buyers might absorb a higher price charged by …rms who have a lower transaction cost. Think of all …rms as being in the same room. 10 / 76 Perfect Competition Free Entry and Exit If all …rms raise their prices and there is pro…t to be made, …rms will keep entering until the price is driven back down. If there were no free exit, …rms might be hesitant to enter the market in case of a bad shock. 11 / 76 Perfect Competition Many markets do not posses all these features, but are for practical purposes still price takers. In these markets, …rms do not deviate signi…cantly from price taking. We still call these markets competitive in practice. 12 / 76 Perfect Competition The most important thing to take away from all this is that a perfectly competitive …rm faces a horizontal demand curve. Lets see how this can occur. 13 / 76 Perfect Competition An individual …rm faces a residual demand curve. This is the market demand not met by other sellers. It is equal to the market demand minus the supply of all other …rms. D r (p ) = D (p ) S o (p ) For example, buyers want to purchase 10,000 bananas and all the other banana …rms sell 9,990 bananas. Residual demand is 10 bananas. 14 / 76 Perfect Competition 15 / 76 Perfect Competition Because the residual demand curve is much ‡atter than the market demand curve, the elasticity of residual demand is much higher than market elasticity If there are n identical …rms, the elasticity of demand facing …rm i is εi = nε (n 1) η o εi is the elasticity facing …rm i. ε is the market elasticity and η o is the elasticity of supply of the other …rms 16 / 76 Perfect Competition EXAMPLE Suppose the market elasticity of demand is 1.5 There are 10 …rms in the market and the elasticity of supply is 4. What is the elasticity of demand facing …rm i? What is the interpretation behind this? What happens when we increase the number of …rms in the market? 17 / 76 Perfect Competition As the number of …rms in the market increases, we approach a perfectly competitive market. As we approach a perfectly competitive market, the demand curve facing a single …rm gets ‡atter and ‡atter. The key point is that an individual …rm is insigni…cant to what happens in the market. 18 / 76 Perfect Competition Why do we study perfect competition? Many markets are reasonably described as competitive. Easy to model. Once we understand it, we can easily add imperfections to make it more realistic. 19 / 76 Pro…t Maximization To derive the market supply curve, we must know how much each …rm wants to produce. We will …rst look at this in the short-run. The …rm produces an amount such that its pro…ts are maximized. Pro…t is just the di¤erence between total revenue and total cost π = TR TC . Total revenue is the number of units you sell times the price of each unit p q. 20 / 76 Pro…t Maximization Cost is a bit less straightforward. We always refer to economic costs. Economic costs includes opportunity cost, accounting cost do not. It might seem like your business is making money, but working somewhere else might be more pro…table. 21 / 76 Pro…t Maximization There are two steps a …rm must make when …nding its pro…t maximizing level of output. The …rst step is the output decision What level of output, q , maximizes pro…t? 22 / 76 Pro…t Maximization The next step is the shutdown decision Is it more pro…table to produce q or to shut down and produce nothing? 23 / 76 Pro…t Maximization A …rm can use any of the following three equivalent rules to choose how much to produce. RULE 1 Maximize pro…t function Find your pro…t function and …nd the maximum. 24 / 76 Pro…t Maximization 25 / 76 Pro…t Maximization RULE 2 Set marginal pro…t to zero Marginal pro…t is the extra pro…t you get from selling one more unit. When marginal pro…t is zero, we will lose pro…t by increasing or decreasing output (must check second order condition). d π (q ) =0 dq 26 / 76 Two Steps to Maximizing Pro…t-Step One RULE 3 Set marginal revenue to equal to marginal cost Marginal revenue is the additional revenue you get from increasing output. Marginal cost is the addition cost you incur from increasing output. At the optimum, MC (q ) = MR (q ). 27 / 76 Pro…t Maximization These are all exactly the same thing max π (q ) = R (q ) C (q ) d π (q ) dR (q ) dC (q ) = =0 dq dq dq dR (q ) dC (q ) = dq dq 28 / 76 Pro…t Maximization EXAMPLE Suppose the market price is p = 100. Our cost function is C (q ) = 20q + 10q 2 What is the pro…t maximizing level of output? 29 / 76 Pro…t Maximization After you know what q is, all we have to know whether or not we should shut down. Remember that in the short run, we can have sunk …xed costs. If a …rm shuts down in the short run, it still has to pay sunk …xed costs. A …rm might stay in business if it is making a loss if it is covering its sunk …xed costs. 30 / 76 Pro…t Maximization The sunk cost should not play a role in the …rm’s shut down decision. The …rm only needs to make sure its costs are less than the avoidable costs. 31 / 76 Pro…t Maximization Suppose Total Revenue = 5000 Variable Cost = 2000 Sunk Fixed Cost = 6000 Should the …rm shut down? 32 / 76 Pro…t Maximization We just need to compare the pro…t from staying in business versus not (π O is pro…t from staying in business and π SD is pro…t from shutting down). πO π SD = 5000 2000 = 6000 6000 = 3000 The …rm minimizes its losses by staying in business 33 / 76 Competition in the Short Run Okay, we know how much an individual …rm decides its production level. We can use this information to …nd out what total market production and the market price is. First, we need to …nd the supply curve of each individual …rm. 34 / 76 Competition in the Short Run REMEMBER, …rms in competitive markets face a horizontal demand curve. No matter how much an individual …rm sells, the price will not change. The price they get from each unit is constant ) R (q ) = p q. The market price is independent of how much an individual …rm produces. 35 / 76 Competition in the Short Run Because the price is the same no matter how much one …rm dR (q ) produces, marginal revenue is simply MR (q ) = dq = p. The pro…t maximizing level of output occurs where MR (q ) = MC (q ) Therefore the pro…t maximizing level of output occurs where MC (q ) = p 36 / 76 Competition in the Short Run The …rm’s supply curve is the marginal cost curve above the shut-down price. That is, the …rm sees the market price and decides how much to produce according to its marginal cost curve. 37 / 76 Competition in the Short Run EXAMPLE Suppose the shutdown price for a …rm is p = 0. What is the …rms supply curve if the cost function is C (q ) = 2q 2 + q + 12 38 / 76 Competition in the Short Run How do we …nd the shut-down price? At q , we can …nd the …rm’s average pro…t as follows π R = q q C pq = q q C =p q AC For example, If the price is $10 and the average cost of producing each unit is $ 3, your average pro…t is $ 7. 39 / 76 Competition in the Short Run 40 / 76 Competition in the Short Run Remember …rms in the short run only care about covering their variable costs. The …rm can only gain from shutting down if its revenue is less than its short-run variable cost pq < VC (q ) Divide both sides by q to show the …rm shuts down if the market price is less than the minimum of its short-run average variable cost curve p< VC (q ) = AVC q 41 / 76 Competition in the Short Run 42 / 76 Competition in the Short Run We know that …rms will shut down if price is p < AVC We also know that to maximize pro…t the …rm will produce where p = MC (q ) The …rm will shutdown when MC < AVC This occurs at the minimum of the average variable cost curve ) The …rm’s shut down price in the short-run is the minimum of the average variable cost curve. 43 / 76 Competition in the Short Run There are two ways we can …nd the shut-down price in the short-run. 1 Minimize the AVC function and …nd the corresponding price. 2 Find the price where AVC = MC 44 / 76 Competition in the Short Run The supply curve is just the marginal cost curve above the minimum of the average cost curve S (p ) = MC (q ) if p pshutdown 0 if p < pshutdown 45 / 76 Competition in the Short Run 46 / 76 Competition in the Short Run EXAMPLE Suppose the …rm’s cost curve is C (q ) = 100 + 10q 1 q2 + q3 3 What is the …rm’s marginal cost and average variable cost. What is the …rm’s supply curve? What is the shut down price? Will the …rm produce if p = 10? if p = 5? 47 / 76 Competition in the Short Run We saw how to get one …rm’s supply curve The market supply curve is the horizontal sum of all the …rm’s in the markets supply curve In the short run, the number of …rms is …xed at n 48 / 76 Competition in the Short Run Suppose an individual …rm has a supply curve q = 10 + P If there are 10 identical …rms, just multiply q by 10 to get the market supply curve Q = 100 + 10P 49 / 76 Competition in the Short Run The more …rms we have, the ‡atter is the market supply curve 50 / 76 Competition in the Short Run If …rms di¤er, the marginal cost curves will not be identical. The shut down prices of …rms will not be the same either. 51 / 76 Competition in the Short Run 52 / 76 Competition in the Short Run By combining the short-run market supply curve and the market demand curve, we can …nd the short-run equilibrium 53 / 76 Competition in the Short Run In summary... Each …rm will produce the level of output where MC = p. We add up the individual …rm supply curves to get the market supply curve. The market price is determined by the intersection of the market supply curve and the market demand curve. 54 / 76 Competition in the Short Run EXAMPLE Each …rm has a cost function of C (q ) = 10q 2 + q + 100 The market demand curve is D (P ) = 145 10P When there are 100 …rms, what is the equilibrium price? 55 / 76 Competition in the Long Run There are two key di¤erences in between the short and long run 1 There are no sunk …xed costs 2 The number of …rms in the market is not …xed 56 / 76 Competition in the Long Run How much will each …rm produce in the long-run? Once again, …rms select the level of output which maximizes their pro…t. The pro…t maximizing level of output occurs where p = MC . 57 / 76 Competition in the Long Run After determining the pro…t maximizing level of output q , the …rm must decide whether or not to shutdown. In the long run, all costs are variable. Unlike in the short-run, the …rm will shut down if it incurs any losses at all. The …rm will shut down when p < AC . The shut-down price occurs at the minimum of the average cost curve. 58 / 76 Competition in the Long Run There are two ways we can …nd the shut-down price in the long-run. 1 Minimize the AC function and …nd the corresponding price. 2 Find the price where AC = MC 59 / 76 Competition in the Long Run Therefore, the supply curve of an individual …rm in the long-run is the marginal cost curve above the minimum of the average curve. S (p ) = MC (q ) if p pshutdown 0 if p < pshutdown 60 / 76 Competition in the Long Run EXAMPLE What is the supply curve for a …rm in the long-run with the cost function: C (q ) = 40q q 2 + .01q 3 61 / 76 Competition in the Long Run The market supply curve is once again the horizontal sum of all …rms’ supply curves. In the short-run, the number of …rms is …xed, but …rms can enter or leave the market in the long run. 62 / 76 Competition in the Long Run If there are pro…ts to be made, …rms will enter the market as there are no barriers in perfect competition. This will cause the market supply curve to shift and the market price to fall. If there is negative pro…t, …rms will exit. The number of …rms is determined by π = 0. 63 / 76 Competition in the Long Run Firms make zero pro…t when p = p SD where p SD is the shutdown price. The shutdown price occurs at the minimum of the average cost curve. Therefore, the market price will always occur at the minimum of the average cost curve. 64 / 76 Competition in the Long Run EXAMPLE Draw the market supply and demand curves in one graph next to a graph showing an individual …rms’s average/marginal cost curves. Identify two market prices, p1 and p2 . At price p1 , …rms will enter the market and at price p2 , …rms will exit the market. 65 / 76 Competition in the Long Run Suppose all …rms have an identical cost curve C (q ) = 40q q 2 + .01q 3 Market demand is D (P ) = 25, 000 1000P 66 / 76 Competition in the Long Run We have three equilibrium conditions in the long run. P is the market price and n is the number of …rms. 1 Pro…t Maximization P = MC ! P = 40 2 Zero Pro…t P = AC ! P = 40 3 2q + .03q 2 q + .01q 2 Supply equals demand nq = 25, 000 1000P 67 / 76 Competition in the Long Run Combine equation 1 and equation 2 to …nd how much each …rm will produce. 40 2q + .03q 2 = 40 q + .01q 2 q = 50 Plug 50 into the average cost curve to …nd the market price will be $15. Plug 15 into the demand curve to see that 10,000 units will be produced. There will be 10,000 / 50 = 200 …rms in the market. 68 / 76 Competition in the Long Run The long run market supply curve is ‡at at the minimum long run average cost curve i¤ input prices are constant. …rms have identical costs. 69 / 76 Competition in the Long Run 70 / 76 Competition in the Long Run Remember how we said there is no such thing as the law of supply? The supply curve can slope upwards or downwards if the previous two conditions are not met. 71 / 76 Competition in the Long Run If entry is limited, the market supply curve will slop upward. Individual …rms have upward sloping supply curves. The only way to increase output is for existing …rms to produce more. 72 / 76 Competition in the Long Run If …rms di¤er in their costs, the market supply curve will also slope upwards. Some …rms will enter the market at lower prices than others. 73 / 76 Competition in the Long Run If the number of co¤ee shops increases, we could expect the price of co¤ee beans to increase. This will also cause the market supply curve to be upward sloping. It is also possible for input prices to decrease with output (economies of scale). This will cause the supply curve to be downward sloping. 74 / 76 Summary What are the conditions under which …rms are price takers? What is the residual demand curve? The …rm will shut down so long as the price is greater than what? The supply curve is the _____ above _____. 75 / 76 Summary How do you determine the market price in the long-run? How do you determine the number of …rms in the long-run? When will the long-run market supply curve slope upwards? When will the long-run market supply curve slope upwards? 76 / 76