# How Perfectly Competitive Firms Make Decisions

How Perfectly Competitive Firms Make Output Decisions By the end of this section, you will be able to:

• Calculate profits by comparing total revenue and total cost • Identify profits and losses with the average cost curve • Explain the shutdown point • Determine the price at which a firm should continue producing in the short run

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A perfectly competitive firm has only one major decision to make—namely, what quantity to produce. To understand why this is so, consider a different way of writing out the basic definition of profit:

Profi = Total revenue − Total cost = (Price)(Quantity produced) − (Average cost)(Quantity produced)

Since a perfectly competitive firm must accept the price for its output as determined by the product’s market demand and supply, it cannot choose the price it charges. This is already determined in the profit equation, and so the perfectly competitive firm can sell any number of units at exactly the same price. It implies that the firm faces a perfectly elastic demand curve for its product: buyers are willing to buy any number of units of output from the firm at the market price. When the perfectly competitive firm chooses what quantity to produce, then this quantity—along with the prices prevailing in the market for output and inputs—will determine the firm’s total revenue, total costs, and ultimately, level of profits.

Determining the Highest Profit by Comparing Total Revenue and Total Cost A perfectly competitive firm can sell as large a quantity as it wishes, as long as it accepts the prevailing market price. Total revenue is going to increase as the firm sells more, depending on the price of the product and the number of units sold. If you increase the number of units sold at a given price, then total revenue will increase. If the price of the product increases for every unit sold, then total revenue also increases. As an example of how a perfectly competitive firm decides what quantity to produce, consider the case of a small farmer who produces raspberries and sells them

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frozen for \$4 per pack. Sales of one pack of raspberries will bring in \$4, two packs will be \$8, three packs will be \$12, and so on. If, for example, the price of frozen raspberries doubles to \$8 per pack, then sales of one pack of raspberries will be \$8, two packs will be \$16, three packs will be \$24, and so on.

Total revenue and total costs for the raspberry farm, broken down into fixed and variable costs, are shown in Table 8.1 and also appear in Figure 8.2. The horizontal axis shows the quantity of frozen raspberries produced in packs; the vertical axis shows both total revenue and total costs, measured in dollars. The total cost curve intersects with the vertical axis at a value that shows the level of fixed costs, and then slopes upward. All these cost curves follow the same characteristics as the curves covered in the Cost and Industry Structure chapter.

Figure 8.2 Total Cost and Total Revenue at the Raspberry Farm Total revenue for a perfectly competitive firm is a straight line sloping up. The slope is equal to the price of the good. Total cost also slopes up, but with some curvature. At higher levels of output, total cost begins to slope upward more steeply because of diminishing marginal returns. The maximum profit will occur at the quantity where the gap of total revenue over total cost is largest.

Quantity (Q)

Total Cost (TC)

Fixed Cost (FC)

Variable Cost (VC)

Total Revenue (TR) Profit

0 \$62 \$62 – \$0 −\$62

10 \$90 \$62 \$28 \$40 −\$50

20 \$110 \$62 \$48 \$80 −\$30

30 \$126 \$62 \$64 \$120 −\$6

40 \$144 \$62 \$82 \$160 \$16

50 \$166 \$62 \$104 \$200 \$34

60 \$192 \$62 \$130 \$240 \$48

70 \$224 \$62 \$162 \$280 \$56

80 \$264 \$62 \$202 \$320 \$56

90 \$324 \$62 \$262 \$360 \$36

100 \$404 \$62 \$342 \$400 −\$4

Table 8.1 Total Cost and Total Revenue at the Raspberry Farm

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Based on its total revenue and total cost curves, a perfectly competitive firm like the raspberry farm can calculate the quantity of output that will provide the highest level of profit. At any given quantity, total revenue minus total cost will equal profit. One way to determine the most profitable quantity to produce is to see at what quantity total revenue exceeds total cost by the largest amount. On Figure 8.2, the vertical gap between total revenue and total cost represents either profit (if total revenues are greater that total costs at a certain quantity) or losses (if total costs are greater that total revenues at a certain quantity). In this example, total costs will exceed total revenues at output levels from 0 to 40, and so over this range of output, the firm will be making losses. At output levels from 50 to 80, total revenues exceed total costs, so the firm is earning profits. But then at an output of 90 or 100, total costs again exceed total revenues and the firm is making losses. Total profits appear in the final column of Table 8.1. The highest total profits in the table, as in the figure that is based on the table values, occur at an output of 70–80, when profits will be \$56.

A higher price would mean that total revenue would be higher for every quantity sold. A lower price would mean that total revenue would be lower for every quantity sold. What happens if the price drops low enough so that the total revenue line is completely below the total cost curve; that is, at every level of output, total costs are higher than total revenues? In this instance, the best the firm can do is to suffer losses. But a profit-maximizing firm will prefer the quantity of output where total revenues come closest to total costs and thus where the losses are smallest.

(Later we will see that sometimes it will make sense for the firm to shutdown, rather than stay in operation producing output.)

Comparing Marginal Revenue and Marginal Costs Firms often do not have the necessary data they need to draw a complete total cost curve for all levels of production. They cannot be sure of what total costs would look like if they, say, doubled production or cut production in half, because they have not tried it. Instead, firms experiment. They produce a slightly greater or lower quantity and observe how profits are affected. In economic terms, this practical approach to maximizing profits means looking at how changes in production affect marginal revenue and marginal cost.

Figure 8.3 presents the marginal revenue and marginal cost curves based on the total revenue and total cost in Table 8.1. The marginal revenue curve shows the additional revenue gained from selling one more unit. As mentioned before, a firm in perfect competition faces a perfectly elastic demand curve for its product—that is, the firm’s demand curve is a horizontal line drawn at the market price level. This also means that the firm’s marginal revenue curve is the same as the firm’s demand curve: Every time a consumer demands one more unit, the firm sells one more unit and revenue goes up by exactly the same amount equal to the market price. In this example, every time a pack of frozen raspberries is sold, the firm’s revenue increases by \$4. Table 8.2 shows an example of this. This condition only holds for price taking firms in perfect competition where:

marginal revenue = price

The formula for marginal revenue is:

marginal revenue = change in total revenuechange in quantity

Price Quantity Total Revenue Marginal Revenue

\$4 1 \$4 –

\$4 2 \$8 \$4

\$4 3 \$12 \$4

\$4 4 \$16 \$4

Table 8.2

Notice that marginal revenue does not change as the firm produces more output. That is because the price is determined by supply and demand and does not change as the farmer produces more (keeping in mind that, due to

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the relative small size of each firm, increasing their supply has no impact on the total market supply where price is determined).

Since a perfectly competitive firm is a price taker, it can sell whatever quantity it wishes at the market-determined price. Marginal cost, the cost per additional unit sold, is calculated by dividing the change in total cost by the change in quantity. The formula for marginal cost is:

marginal cost = change in total costchange in quantity

Ordinarily, marginal cost changes as the firm produces a greater quantity.

In the raspberry farm example, shown in Figure 8.3, Figure 8.4 and Table 8.3, marginal cost at first declines as production increases from 10 to 20 to 30 packs of raspberries—which represents the area of increasing marginal returns that is not uncommon at low levels of production. But then marginal costs start to increase, displaying the typical pattern of diminishing marginal returns. If the firm is producing at a quantity where MR > MC, like 40 or 50 packs of raspberries, then it can increase profit by increasing output because the marginal revenue is exceeding the marginal cost. If the firm is producing at a quantity where MC > MR, like 90 or 100 packs, then it can increase profit by reducing output because the reductions in marginal cost will exceed the reductions in marginal revenue. The firm’s profit-maximizing choice of output will occur where MR = MC (or at a choice close to that point). You will notice that what occurs on the production side is exemplified on the cost side. This is referred to as duality.

Figure 8.3 Marginal Revenues and Marginal Costs at the Raspberry Farm: Individual Farmer For a perfectly competitive firm, the marginal revenue (MR) curve is a horizontal straight line because it is equal to the price of the good, which is determined by the market, shown in Figure 8.4. The marginal cost (MC) curve is sometimes first downward-sloping, if there is a region of increasing marginal returns at low levels of output, but is eventually upward- sloping at higher levels of output as diminishing marginal returns kick in.

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Figure 8.4 Marginal Revenues and Marginal Costs at the Raspberry Farm: Raspberry Market The equilibrium price of raspberries is determined through the interaction of market supply and market demand at \$4.00.

Quantity TotalCost Fixed Cost

Variable Cost

Marginal Cost

Total Revenue

Marginal Revenue

0 \$62 \$62 – – – –

10 \$90 \$62 \$28 \$2.80 \$40 \$4.00

20 \$110 \$62 \$48 \$2.00 \$80 \$4.00

30 \$126 \$62 \$64 \$1.60 \$120 \$4.00

40 \$144 \$62 \$82 \$1.80 \$160 \$4.00

50 \$166 \$62 \$104 \$2.20 \$200 \$4.00

60 \$192 \$62 \$130 \$2.60 \$240 \$4.00

70 \$224 \$62 \$162 \$3.20 \$280 \$4.00

80 \$264 \$62 \$202 \$4.00 \$320 \$4.00

90 \$324 \$62 \$262 \$6.00 \$360 \$4.00

100 \$404 \$62 \$342 \$8.00 \$400 \$4.00

Table 8.3 Marginal Revenues and Marginal Costs at the Raspberry Farm

In this example, the marginal revenue and marginal cost curves cross at a price of \$4 and a quantity of 80 produced. If the farmer started out producing at a level of 60, and then experimented with increasing production to 70, marginal revenues from the increase in production would exceed marginal costs—and so profits would rise. The farmer has an incentive to keep producing. From a level of 70 to 80, marginal cost and marginal revenue are equal so profit doesn’t change. If the farmer then experimented further with increasing production from 80 to 90, he would find that marginal costs from the increase in production are greater than marginal revenues, and so profits would decline.

The profit-maximizing choice for a perfectly competitive firm will occur where marginal revenue is equal to marginal cost—that is, where MR = MC. A profit-seeking firm should keep expanding production as long as MR > MC. But at the level of output where MR = MC, the firm should recognize that it has achieved the highest possible level of economic profits. (In the example above, the profit maximizing output level is between 70 and 80 units of output, but

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the firm will not know they’ve maximized profit until they reach 80, where MR = MC.) Expanding production into the zone where MR < MC will only reduce economic profits. Because the marginal revenue received by a perfectly competitive firm is equal to the price P, so that P = MR, the profit-maximizing rule for a perfectly competitive firm can also be written as a recommendation to produce at the quantity where P = MC.

Profits and Losses with the Average Cost Curve Does maximizing profit (producing where MR = MC) imply an actual economic profit? The answer depends on the relationship between price and average total cost. If the price that a firm charges is higher than its average cost of production for that quantity produced, then the firm will earn profits. Conversely, if the price that a firm charges is lower than its average cost of production, the firm will suffer losses. You might think that, in this situation, the farmer may want to shut down immediately. Remember, however, that the firm has already paid for fixed costs, such as equipment, so it may continue to produce and incur a loss. Figure 8.5 illustrates three situations: (a) where price intersects marginal cost at a level above the average cost curve, (b) where price intersects marginal cost at a level equal to the average cost curve, and (c) where price intersects marginal cost at a level below the average cost curve.

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Figure 8.5 Price and Average Cost at the Raspberry Farm In (a), price intersects marginal cost above the average cost curve. Since price is greater than average cost, the firm is making a profit. In (b), price intersects marginal cost at the minimum point of the average cost curve. Since price is equal to average cost, the firm is breaking even. In (c), price intersects marginal cost below the average cost curve. Since price is less than average cost, the firm is making a loss.

First consider a situation where the price is equal to \$5 for a pack of frozen raspberries. The rule for a profit- maximizing perfectly competitive firm is to produce the level of output where Price= MR = MC, so the raspberry farmer will produce a quantity of 90, which is labeled as e in Figure 8.5 (a). Remember that the area of a rectangle is equal to its base multiplied by its height. The farm’s total revenue at this price will be shown by the large shaded rectangle from the origin over to a quantity of 90 packs (the base) up to point E’ (the height), over to the price of \$5, and back to the origin. The average cost of producing 80 packs is shown by point C or about \$3.50. Total costs will be the quantity of 80 times the average cost of \$3.50, which is shown by the area of the rectangle from the origin to a quantity of 90, up to point C, over to the vertical axis and down to the origin. It should be clear from examining the two rectangles that total revenue is greater than total cost. Thus, profits will be the blue shaded rectangle on top.

It can be calculated as:

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profi = total revenue − total cost = (90)(\$5.00) − (90)(\$3.50) = \$135

Or, it can be calculated as:

profi = (price – average cost) × quantity = (\$5.00 – \$3.50) × 90 = \$135

Now consider Figure 8.5 (b), where the price has fallen to \$3.00 for a pack of frozen raspberries. Again, the perfectly competitive firm will choose the level of output where Price = MR = MC, but in this case, the quantity produced will be 70. At this price and output level, where the marginal cost curve is crossing the average cost curve, the price received by the firm is exactly equal to its average cost of production.

The farm’s total revenue at this price will be shown by the large shaded rectangle from the origin over to a quantity of 70 packs (the base) up to point E (the height), over to the price of \$3, and back to the origin. The average cost of producing 70 packs is shown by point C’. Total costs will be the quantity of 70 times the average cost of \$3.00, which is shown by the area of the rectangle from the origin to a quantity of 70, up to point E, over to the vertical axis and down to the origin. It should be clear from that the rectangles for total revenue and total cost are the same. Thus, the firm is making zero profit. The calculations are as follows:

profi = total revenue – total cost = (70)(\$3.00) – (70)(\$3.00) = \$0

Or, it can be calculated as:

profi = (price – average cost)×quantity = (\$3.00 – \$3.00)×70 = \$0

In Figure 8.5 (c), the market price has fallen still further to \$2.00 for a pack of frozen raspberries. At this price, marginal revenue intersects marginal cost at a quantity of 50. The farm’s total revenue at this price will be shown by the large shaded rectangle from the origin over to a quantity of 50 packs (the base) up to point E” (the height), over to the price of \$2, and back to the origin. The average cost of producing 50 packs is shown by point C” or about \$3.30. Total costs will be the quantity of 50 times the average cost of \$3.30, which is shown by the area of the rectangle from the origin to a quantity of 50, up to point C”, over to the vertical axis and down to the origin. It should be clear from examining the two rectangles that total revenue is less than total cost. Thus, the firm is losing money and the loss (or negative profit) will be the rose-shaded rectangle.

The calculations are:

profi = (total revenue – total cost) = (50)(\$2.00) – (50)(\$3.30) = –\$77.50

Or:

profi = (price – average cost) × quantity = (\$1.75 – \$3.30) × 50 = –\$77.50

If the market price received by a perfectly competitive firm leads it to produce at a quantity where the price is greater than average cost, the firm will earn profits. If the price received by the firm causes it to produce at a quantity where price equals average cost, which occurs at the minimum point of the AC curve, then the firm earns zero profits. Finally, if the price received by the firm leads it to produce at a quantity where the price is less than average cost, the firm will earn losses. This is summarized in Table 8.4.

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If… Then…

Price > ATC Firm earns an economic profit

Price = ATC Firm earns zero economic profit

Price < ATC Firm earns a loss

Table 8.4

The Shutdown Point The possibility that a firm may earn losses raises a question: Why can the firm not avoid losses by shutting down and not producing at all? The answer is that shutting down can reduce variable costs to zero, but in the short run, the firm has already paid for fixed costs. As a result, if the firm produces a quantity of zero, it would still make losses because it would still need to pay for its fixed costs. So, when a firm is experiencing losses, it must face a question: should it continue producing or should it shut down?

As an example, consider the situation of the Yoga Center, which has signed a contract to rent space that costs \$10,000 per month. If the firm decides to operate, its marginal costs for hiring yoga teachers is \$15,000 for the month. If the firm shuts down, it must still pay the rent, but it would not need to hire labor. Table 8.5 shows three possible scenarios. In the first scenario, the Yoga Center does not have any clients, and therefore does not make any revenues, in which case it faces losses of \$10,000 equal to the fixed costs. In the second scenario, the Yoga Center has clients that earn the center revenues of \$10,000 for the month, but ultimately experiences losses of \$15,000 due to having to hire yoga instructors to cover the classes. In the third scenario, the Yoga Center earns revenues of \$20,000 for the month, but experiences losses of \$5,000.

In all three cases, the Yoga Center loses money. In all three cases, when the rental contract expires in the long run, assuming revenues do not improve, the firm should exit this business. In the short run, though, the decision varies depending on the level of losses and whether the firm can cover its variable costs. In scenario 1, the center does not have any revenues, so hiring yoga teachers would increase variable costs and losses, so it should shut down and only incur its fixed costs. In scenario 2, the center’s losses are greater because it does not make enough revenue to offset the increased variable costs plus fixed costs, so it should shut down immediately. If price is below the minimum average variable cost, the firm must shut down. In contrast, in scenario 3 the revenue that the center can earn is high enough that the losses diminish when it remains open, so the center should remain open in the short run.

Scenario 1

If the center shuts down now, revenues are zero but it will not incur any variable costs and would only need to pay fixed costs of \$10,000.

profit = otal revenue–(fi ed costs + variable cost) = 0 –\$10,000 = –\$10,000

Scenario 2

The center earns revenues of \$10,000, and variable costs are \$15,000. The center should shut down now.

profit = otal revenue – (fi ed costs + variable cost) = \$10,000 – (\$10,000 + \$15,000) = –\$15,000

Table 8.5 Should the Yoga Center Shut Down Now or Later?

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Scenario 3

The center earns revenues of \$20,000, and variable costs are \$15,000. The center should continue in business.

profit = otal revenue – (fi ed costs + variable cost) = \$20,000 – (\$10,000 + \$15,000) = –\$5,000

Table 8.5 Should the Yoga Center Shut Down Now or Later?

This example suggests that the key factor is whether a firm can earn enough revenues to cover at least its variable costs by remaining open. Let’s return now to our raspberry farm. Figure 8.6 illustrates this lesson by adding the average variable cost curve to the marginal cost and average cost curves. At a price of \$2.20 per pack, as shown in Figure 8.6 (a), the farm produces at a level of 50. It is making losses of \$56 (as explained earlier), but price is above average variable cost and so the firm continues to operate. However, if the price declined to \$1.80 per pack, as shown in Figure 8.6 (b), and if the firm applied its rule of producing where P = MR = MC, it would produce a quantity of 40. This price is below average variable cost for this level of output. If the farmer cannot pay workers (the variable costs), then it has to shut down. At this price and output, total revenues would be \$72 (quantity of 40 times price of \$1.80) and total cost would be \$144, for overall losses of \$72. If the farm shuts down, it must pay only its fixed costs of \$62, so shutting down is preferable to selling at a price of \$1.80 per pack.

Figure 8.6 The Shutdown Point for the Raspberry Farm In (a), the farm produces at a level of 50. It is making losses of \$56, but price is above average variable cost, so it continues to operate. In (b), total revenues are \$72 and total cost is \$144, for overall losses of \$72. If the farm shuts down, it must pay only its fixed costs of \$62. Shutting down is preferable to selling at a price of \$1.80 per pack.

Looking at Table 8.6, if the price falls below \$2.05, the minimum average variable cost, the firm must shut down.

Quantity TotalCost Fixed Cost

Variable Cost

Marginal Cost

Average Cost

Average Variable Cost

0 \$62 \$62 – – – –

10 \$90 \$62 \$28 \$2.80 \$9.00 \$2.80

Table 8.6 Cost of Production for the Raspberry Farm

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Quantity TotalCost Fixed Cost

Variable Cost

Marginal Cost

Average Cost

Average Variable Cost

20 \$110 \$62 \$48 \$2.00 \$5.50 \$2.40

30 \$126 \$62 \$64 \$1.60 \$4.20 \$2.13

40 \$144 \$62 \$82 \$1.80 \$3.60 \$2.05

50 \$166 \$62 \$104 \$2.20 \$3.32 \$2.08

60 \$192 \$62 \$130 \$2.60 \$3.20 \$2.16

70 \$224 \$62 \$162 \$3.20 \$3.20 \$2.31

80 \$264 \$62 \$202 \$4.00 \$3.30 \$2.52

90 \$324 \$62 \$262 \$6.00 \$3.60 \$2.91

100 \$404 \$62 \$342 \$8.00 \$4.04 \$3.42

Table 8.6 Cost of Production for the Raspberry Farm

The intersection of the average variable cost curve and the marginal cost curve, which shows the price where the firm would lack enough revenue to cover its variable costs, is called the shutdown point. If the perfectly competitive firm can charge a price above the shutdown point, then the firm is at least covering its average variable costs. It is also making enough revenue to cover at least a portion of fixed costs, so it should limp ahead even if it is making losses in the short run, since at least those losses will be smaller than if the firm shuts down immediately and incurs a loss equal to total fixed costs. However, if the firm is receiving a price below the price at the shutdown point, then the firm is not even covering its variable costs. In this case, staying open is making the firm’s losses larger, and it should shut down immediately. To summarize, if:

• price < minimum average variable cost, then firm shuts down

• price = minimum average variable cost, then firm stays in business

Short-Run Outcomes for Perfectly Competitive Firms The average cost and average variable cost curves divide the marginal cost curve into three segments, as shown in Figure 8.7. At the market price, which the perfectly competitive firm accepts as given, the profit-maximizing firm chooses the output level where price or marginal revenue, which are the same thing for a perfectly competitive firm, is equal to marginal cost: P = MR = MC.

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Figure 8.7 Profit, Loss, Shutdown The marginal cost curve can be divided into three zones, based on where it is crossed by the average cost and average variable cost curves. The point where MC crosses AC is called the zero- profit point. If the firm is operating at a level of output where the market price is at a level higher than the zero-profit point, then price will be greater than average cost and the firm is earning profits. If the price is exactly at the zero- profit point, then the firm is making zero profits. If price falls in the zone between the shutdown point and the zero- profit point, then the firm is making losses but will continue to operate in the short run, since it is covering its variable costs. However, if price falls below the price at the shutdown point, then the firm will shut down immediately, since it is not even covering its variable costs.

First consider the upper zone, where prices are above the level where marginal cost (MC) crosses average cost (AC) at the zero profit point. At any price above that level, the firm will earn profits in the short run. If the price falls exactly on the zero profit point where the MC and AC curves cross, then the firm earns zero profits. If a price falls into the zone between the zero profit point, where MC crosses AC, and the shutdown point, where MC crosses AVC, the firm will be making losses in the short run—but since the firm is more than covering its variable costs, the losses are smaller than if the firm shut down immediately. Finally, consider a price at or below the shutdown point where MC crosses AVC. At any price like this one, the firm will shut down immediately, because it cannot even cover its variable costs.

Marginal Cost and the Firm’s Supply Curve For a perfectly competitive firm, the marginal cost curve is identical to the firm’s supply curve starting from the minimum point on the average variable cost curve. To understand why this perhaps surprising insight holds true, first think about what the supply curve means. A firm checks the market price and then looks at its supply curve to decide what quantity to produce. Now, think about what it means to say that a firm will maximize its profits by producing at the quantity where P = MC. This rule means that the firm checks the market price, and then looks at its marginal cost to determine the quantity to produce—and makes sure that the price is greater than the minimum average variable cost. In other words, the marginal cost curve above the minimum point on the average variable cost curve becomes the firm’s supply curve.

Watch this video (http://openstaxcollege.org/l/foodprice) that addresses how drought in the United States can impact food prices across the world. (Note that the story on the drought is the second one in the news report; you need to let the video play through the first story in order to watch the story on the drought.)

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As discussed in the chapter on Demand and Supply, many of the reasons that supply curves shift relate to underlying changes in costs. For example, a lower price of key inputs or new technologies that reduce production costs cause supply to shift to the right; in contrast, bad weather or added government regulations can add to costs of certain goods in a way that causes supply to shift to the left. These shifts in the firm’s supply curve can also be interpreted as shifts of the marginal cost curve. A shift in costs of production that increases marginal costs at all levels of output—and shifts MC to the left—will cause a perfectly competitive firm to produce less at any given market price. Conversely, a shift in costs of production that decreases marginal costs at all levels of output will shift MC to the right and as a result, a competitive firm will choose to expand its level of output at any given price. The following Work It Out feature will walk you through an example.

At What Price Should the Firm Continue Producing in the Short Run? To determine the short-run economic condition of a firm in perfect competition, follow the steps outlined below. Use the data shown in Table 8.7.

Q P TFC TVC TC AVC ATC MC TR Profits

0 \$28 \$20 \$0 – – – – – –

1 \$28 \$20 \$20 – – – – – –

2 \$28 \$20 \$25 – – – – – –

3 \$28 \$20 \$35 – – – – – –

4 \$28 \$20 \$52 – – – – – –

5 \$28 \$20 \$80 – – – – – –

Table 8.7

Step 1. Determine the cost structure for the firm. For a given total fixed costs and variable costs, calculate total cost, average variable cost, average total cost, and marginal cost. Follow the formulas given in the Cost and Industry Structure chapter. These calculations are shown in Table 8.8.

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Q P TFC TVC TC(TFC+TVC) AVC

(TVC/Q) ATC

(TC/Q)

MC (TC2−TC1)/

(Q2−Q1)

0 \$28 \$20 \$0 \$20+\$0=\$20 – – –

1 \$28 \$20 \$20 \$20+\$20=\$40 \$20/1=\$20.00 \$40/1=\$40.00 (\$40−\$20)/ (1−0)= \$20

2 \$28 \$20 \$25 \$20+\$25=\$45 \$25/2=\$12.50 \$45/2=\$22.50 (\$45−\$40)/ (2−1)= \$5

3 \$28 \$20 \$35 \$20+\$35=\$55 \$35/3=\$11.67 \$55/3=\$18.33 (\$55−\$45)/ (3−2)= \$10

4 \$28 \$20 \$52 \$20+\$52=\$72 \$52/4=\$13.00 \$72/4=\$18.00 (\$72−\$55)/ (4−3)= \$17

5 \$28 \$20 \$80 \$20+\$80=\$100 \$80/5=\$16.00 \$100/5=\$20.00 (\$100−\$72)/ (5−4)= \$28

Table 8.8

Step 2. Determine the market price that the firm receives for its product. This should be given information, as the firm in perfect competition is a price taker. With the given price, calculate total revenue as equal to price multiplied by quantity for all output levels produced. In this example, the given price is \$30. You can see that in the second column of Table 8.9.

Quantity Price Total Revenue (P × Q)

0 \$28 \$28×0=\$0

1 \$28 \$28×1=\$28

2 \$28 \$28×2=\$56

3 \$28 \$28×3=\$84

4 \$28 \$28×4=\$112

5 \$28 \$28×5=\$140

Table 8.9

Step 3. Calculate profits as total cost subtracted from total revenue, as shown in Table 8.10.

Quantity Total Revenue Total Cost Profits (TR−TC)

0 \$0 \$20 \$0−\$20=−\$20

1 \$28 \$40 \$28−\$40=−\$12

2 \$56 \$45 \$56−\$45=\$11

Table 8.10

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Quantity Total Revenue Total Cost Profits (TR−TC)

3 \$84 \$55 \$84−\$55=\$29

4 \$112 \$72 \$112−\$72=\$40

5 \$140 \$100 \$140−\$100=\$40

Table 8.10

Step 4. To find the profit-maximizing output level, look at the Marginal Cost column (at every output level produced), as shown in Table 8.11, and determine where it is equal to the market price. The output level where price equals the marginal cost is the output level that maximizes profits.

Q P TFC TVC TC AVC ATC MC TR Profits

0 \$28 \$20 \$0 \$20 – – – \$0 −\$20

1 \$28 \$20 \$20 \$40 \$20.00 \$40.00 \$20 \$28 −\$12

2 \$28 \$20 \$25 \$45 \$12.50 \$22.50 \$5 \$56 \$11

3 \$28 \$20 \$35 \$55 \$11.67 \$18.33 \$10 \$84 \$29

4 \$28 \$20 \$52 \$72 \$13.00 \$18.00 \$17 \$112 \$40

5 \$28 \$20 \$80 \$100 \$16.40 \$20.40 \$30 \$140 \$40

Table 8.11

Step 5. Once you have determined the profit-maximizing output level (in this case, output quantity 5), you can look at the amount of profits made (in this case, \$40).

Step 6. If the firm is making economic losses, the firm needs to determine whether it produces the output level where price equals marginal revenue and equals marginal cost or it shuts down and only incurs its fixed costs.

Step 7. For the output level where marginal revenue is equal to marginal cost, check if the market price is greater than the average variable cost of producing that output level.

• If P > AVC but P < ATC, then the firm continues to produce in the short-run, making economic losses.

• If P < AVC, then the firm stops producing and only incurs its fixed costs.

In this example, the price of \$28 is greater than the AVC (\$16.40) of producing 5 units of output, so the firm continues producing.

8.3 | Entry and Exit Decisions in the Long Run By the end of this section, you will be able to:

• Explain how entry and exit lead to zero profits in the long run • Discuss the long-run adjustment process

The line between the short run and the long run cannot be defined precisely with a stopwatch, or even with a calendar. It varies according to the specific business. The distinction between the short run and the long run is therefore more technical: in the short run, firms cannot change the usage of fixed inputs, while in the long run, the firm can adjust all factors of production.

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In a competitive market, profits are a red cape that incites businesses to charge. If a business is making a profit in the short run, it has an incentive to expand existing factories or to build new ones. New firms may start production, as well. When new firms enter the industry in response to increased industry profits it is called entry.

Losses are the black thundercloud that causes businesses to flee. If a business is making losses in the short run, it will either keep limping along or just shut down, depending on whether its revenues are covering its variable costs. But in the long run, firms that are facing losses will shut down at least some of their output, and some firms will cease production altogether. The long-run process of reducing production in response to a sustained pattern of losses is called exit. The following Clear It Up feature discusses where some of these losses might come from, and the reasons why some firms go out of business.

Why do firms cease to exist? Can we say anything about what causes a firm to exit an industry? Profits are the measurement that determines whether a business stays operating or not. Individuals start businesses with the purpose of making profits. They invest their money, time, effort, and many other resources to produce and sell something that they hope will give them something in return. Unfortunately, not all businesses are successful, and many new startups soon realize that their “business adventure” must eventually end.

In the model of perfectly competitive firms, those that consistently cannot make money will “exit,” which is a nice, bloodless word for a more painful process. When a business fails, after all, workers lose their jobs, investors lose their money, and owners and managers can lose their dreams. Many businesses fail. The U.S. Small Business Administration indicates that in 2011, 409,040 new firms “entered,” and 470,376 firms failed.

Sometimes a business fails because of poor management or workers who are not very productive, or because of tough domestic or foreign competition. Businesses also fail from a variety of causes that might best be summarized as bad luck. For example, conditions of demand and supply in the market shift in an unexpected way, so that the prices that can be charged for outputs fall or the prices that need to be paid for inputs rise. With millions of businesses in the U.S. economy, even a small fraction of them failing will affect many people—and business failures can be very hard on the workers and managers directly involved. But from the standpoint of the overall economic system, business exits are sometimes a necessary evil if a market-oriented system is going to offer a flexible mechanism for satisfying customers, keeping costs low, and inventing new products.

How Entry and Exit Lead to Zero Profits in the Long Run No perfectly competitive firm acting alone can affect the market price. However, the combination of many firms entering or exiting the market will affect overall supply in the market. In turn, a shift in supply for the market as a whole will affect the market price. Entry and exit to and from the market are the driving forces behind a process that, in the long run, pushes the price down to minimum average total costs so that all firms are earning a zero profit.

To understand how short-run profits for a perfectly competitive firm will evaporate in the long run, imagine the following situation. The market is in long-run equilibrium, where all firms earn zero economic profits producing the output level where P = MR = MC and P = AC. No firm has the incentive to enter or leave the market. Let’s say that the product’s demand increases, and with that, the market price goes up. The existing firms in the industry are now facing a higher price than before, so they will increase production to the new output level where P = MR = MC.

This will temporarily make the market price rise above the average cost curve, and therefore, the existing firms in the market will now be earning economic profits. However, these economic profits attract other firms to enter the market. Entry of many new firms causes the market supply curve to shift to the right. As the supply curve shifts to the right, the market price starts decreasing, and with that, economic profits fall for new and existing firms. As long as there are still profits in the market, entry will continue to shift supply to the right. This will stop whenever the market price is driven down to the zero-profit level, where no firm is earning economic profits.

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Short-run losses will fade away by reversing this process. Say that the market is in long-run equilibrium. This time, instead, demand decreases, and with that, the market price starts falling. The existing firms in the industry are now facing a lower price than before, and as it will be below the average cost curve, they will now be making economic losses. Some firms will continue producing where the new P = MR = MC, as long as they are able to cover their average variable costs. Some firms will have to shut down immediately as they will not be able to cover their average variable costs, and will then only incur their fixed costs, minimizing their losses. Exit of many firms causes the market supply curve to shift to the left. As the supply curve shifts to the left, the market price starts rising, and economic losses start to be lower. This process ends whenever the market price rises to the zero-profit level, where the existing firms are no longer losing money and are at zero profits again. Thus, while a perfectly competitive firm can earn profits in the short run, in the long run the process of entry will push down prices until they reach the zero-profit level. Conversely, while a perfectly competitive firm may earn losses in the short run, firms will not continually lose money. In the long run, firms making losses are able to escape from their fixed costs, and their exit from the market will push the price back up to the zero-profit level. In the long run, this process of entry and exit will drive the price in perfectly competitive markets to the zero-profit point at the bottom of the AC curve, where marginal cost crosses average cost.

The Long-Run Adjustment and Industry Types Whenever there are expansions in an industry, costs of production for the existing and new firms could either stay the same, increase, or even decrease. Therefore, we can categorize an industry as being (1) a constant cost industry (as demand increases, the cost of production for firms stays the same), (2) an increasing cost industry (as demand increases, the cost of production for firms increases), or (3) a decreasing cost industry (as demand increases the costs of production for the firms decreases).

For a constant cost industry, whenever there is an increase in market demand and price, then the supply curve shifts to the right with new firms’ entry and stops at the point where the new long-run equilibrium intersects at the same market price as before. But why will costs remain the same? In this type of industry, the supply curve is very elastic. Firms can easily supply any quantity that consumers demand. In addition, there is a perfectly elastic supply of inputs—firms can easily increase their demand for employees, for example, with no increase to wages. Tying in to our Bring it Home discussion, an increased demand for ethanol in recent years has caused the demand for corn to increase. Consequently, many farmers switched from growing wheat to growing corn. Agricultural markets are generally good examples of constant cost industries.

For an increasing cost industry, as the market expands, the old and new firms experience increases in their costs of production, which makes the new zero-profit level intersect at a higher price than before. Here companies may have to deal with limited inputs, such as skilled labor. As the demand for these workers rise, wages rise and this increases the cost of production for all firms. The industry supply curve in this type of industry is more inelastic.

For a decreasing cost industry, as the market expands, the old and new firms experience lower costs of production, which makes the new zero-profit level intersect at a lower price than before. In this case, the industry and all the firms in it are experiencing falling average total costs. This can be due to an improvement in technology in the entire industry or an increase in the education of employees. High tech industries may be a good example of a decreasing cost market.

Figure 8.8 (a) presents the case of an adjustment process in a constant cost industry. Whenever there are output expansions in this type of industry, the long-run outcome implies more output produced at exactly the same original price. Note that supply was able to increase to meet the increased demand. When we join the before and after long-run equilibriums, the resulting line is the long run supply (LRS) curve in perfectly competitive markets. In this case, it is a flat curve. Figure 8.8 (b) and Figure 8.8 (c) present the cases for an increasing cost and decreasing cost industry, respectively. For an increasing cost industry, the LRS is upward sloping, while for a decreasing cost industry, the LRS is downward sloping.

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Figure 8.8 Adjustment Process in a Constant-Cost Industry In (a), demand increased and supply met it. Notice that the supply increase is equal to the demand increase. The result is that the equilibrium price stays the same as quantity sold increases. In (b), notice that sellers were not able to increase supply as much as demand. Some inputs were scarce, or wages were rising. The equilibrium price rises. In (c), sellers easily increased supply in response to the demand increase. Here, new technology or economies of scale caused the large increase in supply, resulting in declining equilibrium price.

8.4 | Efficiency in Perfectly Competitive Markets By the end of this section, you will be able to:

• Apply concepts of productive efficiency and allocative efficiency to perfectly competitive markets • Compare the model of perfect competition to real-world markets

When profit-maximizing firms in perfectly competitive markets combine with utility-maximizing consumers, something remarkable happens: the resulting quantities of outputs of goods and services demonstrate both productive and allocative efficiency (terms that were first introduced in (Choice in a World of Scarcity) .

Productive efficiency means producing without waste, so that the choice is on the production possibility frontier. In the long run in a perfectly competitive market, because of the process of entry and exit, the price in the market is equal to the minimum of the long-run average cost curve. In other words, goods are being produced and sold at the lowest possible average cost.

Allocative efficiency means that among the points on the production possibility frontier, the point that is chosen is socially preferred—at least in a particular and specific sense. In a perfectly competitive market, price will be equal to the marginal cost of production. Think about the price that is paid for a good as a measure of the social benefit received for that good; after all, willingness to pay conveys what the good is worth to a buyer. Then think about the marginal cost of producing the good as representing not just the cost for the firm, but more broadly as the social cost of producing that good. When perfectly competitive firms follow the rule that profits are maximized by producing at the quantity where price is equal to marginal cost, they are thus ensuring that the social benefits received from producing a good are in line with the social costs of production.

To explore what is meant by allocative efficiency, it is useful to walk through an example. Begin by assuming that the market for wholesale flowers is perfectly competitive, and so P = MC. Now, consider what it would mean if firms in that market produced a lesser quantity of flowers. At a lesser quantity, marginal costs will not yet have increased as much, so that price will exceed marginal cost; that is, P > MC. In that situation, the benefit to society as a whole of producing additional goods, as measured by the willingness of consumers to pay for marginal units of a good, would be higher than the cost of the inputs of labor and physical capital needed to produce the marginal good. In other words, the gains to society as a whole from producing additional marginal units will be greater than the costs.

Conversely, consider what it would mean if, compared to the level of output at the allocatively efficient choice when P = MC, firms produced a greater quantity of flowers. At a greater quantity, marginal costs of production will have increased so that P < MC. In that case, the marginal costs of producing additional flowers is greater than the benefit

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to society as measured by what people are willing to pay. For society as a whole, since the costs are outstripping the benefits, it will make sense to produce a lower quantity of such goods.

When perfectly competitive firms maximize their profits by producing the quantity where P = MC, they also assure that the benefits to consumers of what they are buying, as measured by the price they are willing to pay, is equal to the costs to society of producing the marginal units, as measured by the marginal costs the firm must pay—and thus that allocative efficiency holds.

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