1. Principles of Microeconomics
PowerPoint Presentations for
Principles of Microeconomics
Sixth Canadian Edition
by Mankiw/Kneebone/McKenzie
Adapted for the
Sixth Canadian Edition by
Marc Prud’homme
University of Ottawa

2. the costs of production
Chapter 13
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3. the costs of production
In this chapter and the ones that follow, we examine firm behaviour in more detail.
This topic will give you a better understanding of what decisions lie behind the supply curve in a market.
In addition, it will introduce you to a part of economics called industrial organization: the study of how firms’ decisions regarding prices and quantities depend on the market conditions they face.
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4. the costs of production
The town in which you live, for instance, may have several pizzerias but only one cable television company.
How does this difference in the number of firms affect the prices in these markets and the efficiency of the market outcomes?
The field of industrial organization addresses exactly this question.
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WHAT are costs?
We begin our discussion of costs at Hungry Helen’s Cookie Factory.
Helen, the owner of the firm, buys flour, sugar, chocolate chips, and other cookie ingredients.
She also buys the mixers and ovens and hires workers to run this equipment.
She then sells the resulting cookies to consumers.
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6. Total Revenue, Total Cost, and Profit
Total revenue (for a firm): the amount a firm receives for the sale of its output
Total cost: the market value of the inputs a firm uses in production
Profit: total revenue minus total cost
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7. Costs as Opportunity Costs
The cost of something is what you give up to get it. Recall that the opportunity cost of an item refers to all those things that must be forgone to acquire that item.
When economists speak of a firm’s cost of production, they include all the opportunity costs of making its output of goods and services.
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8. Costs as Opportunity Costs
Explicit costs: input costs that require an outlay of money by the firm
Implicit costs: input costs that do not require an outlay of money by the firm
By contrast, some of a firm’s opportunity costs, called implicit costs, do not require a cash outlay. Imagine that Helen is skilled with computers and could earn $100 per hour working as a programmer. For every hour that Helen works at her cookie factory, she gives up $100 in income, and this forgone income is also part of her costs. This distinction between explicit and implicit costs highlights an important difference between how economists and accountants analyze a business. Economists are interested in studying how firms make production and pricing decisions. Because these decisions are based on both explicit and implicit costs, economists include both when measuring a firm’s costs. By contrast, accountants have the job of keeping track of the money that flows into and out of firms. As a result, they measure the explicit costs but often ignore the implicit costs.
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9. The Cost of Capital as an Opportunity Cost
An important implicit cost of almost every business is the opportunity cost of the financial capital that has been invested in the business.
Helen used $ of her savings to buy her factory.
If Helen had instead left this money in a savings account that pays an interest rate of 5 percent, she would have earned $ per year.
This forgone $ is one of the implicit opportunity costs of Helen’s business.
An economist views the $ in interest income that Helen gives up every year as a cost of her business, even though it is an implicit cost. Helen’s accountant, however, will not show this $ as a cost because no money flows out of the business to pay for it.
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10. Economic Profit versus Accounting Profit
Because economists and accountants measure costs differently, they also measure profit differently.
An economist measures a firm’s economic profit as the firm’s total revenue minus all the opportunity costs (explicit and implicit) of producing the goods and services sold.
An accountant measures the firm’s accounting profit as the firm’s total revenue minus only the firm’s explicit costs.
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11. FIGURE 13.1: Economists versus Accountants
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Farmer McDonald gives banjo lessons for $20 an hour. One day he spends 10 hours planting $100 worth of seeds on his farm.
What opportunity cost has he incurred? What cost would his accountant measure?
If these seeds will yield $200 worth of crops, does McDonald earn an accounting profit?
Does he earn an economic profit?
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production AND COSTS
In the analysis that follows, we make an important simplifying assumption: We assume that the size of Helen’s factory is fixed and that Helen can vary the quantity of cookies produced only by changing the number of workers.
This assumption is realistic in the short run but not in the long run.
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14. The Production Function
Production function: the relationship between the quantity of inputs used to make a good and the quantity of output of that good
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TABLE 13.1: A Production Function and Total Cost: Hungry Helen’s Cookie Factory
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16. FIGURE 13.2: Hungry Helen’s Cookie Factory
Production Function
Total-Cost Curve
(a) Hungry Helen’s Production Function
A production function shows the relationship between the number of workers hired and the quantity of output produced. Here the number of workers hired (on the horizontal axis) is from the first column in Table 13.1, and the quantity of output produced (on the vertical axis) is from the second column. The production function gets flatter as the number of workers increases, which reflects diminishing marginal product.
(b) Hungry Helen’s Total-Cost Curve
A total-cost curve shows the relationship between the quantity of output produced and total cost of production. Here the quantity of output produced (on the horizontal axis) is from the second column in Table 13.1, and the total cost (on the vertical axis) is from the sixth column. The total-cost curve gets steeper as the quantity of output increases because of diminishing marginal product.
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17. The Production Function
Marginal product: the increase in output that arises from an additional unit of input
Diminishing marginal product: the property whereby the marginal product of an input declines as the quantity of the input increases
At first, when only a few workers are hired, they have easy access to Helen’s kitchen equipment. As the number of workers increases, additional workers have to share equipment and work in more crowded conditions. Eventually, the kitchen is so crowded that the workers start getting in each other’s way. Hence, as more and more workers are hired, each additional worker contributes fewer additional cookies to total production. Diminishing marginal product is also apparent in Figure The production function’s slope (rise over run) tells us the change in Helen’s output of cookies (rise) for each additional input of labour (run). That is, the slope of the production function measures the marginal product of a worker. As the number of workers increases, the marginal product declines, and the production function becomes flatter.
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18. From the Production Function to the Total-Cost Curve
The last three columns of Table 13.1 show Helen’s cost of producing cookies.
The cost of Helen’s factory is $30 per hour, and the cost of a worker is $10 per hour.
If she hires one worker, her total cost is $40.
If she hires two workers, her total cost is $50, and so on.
With this information, the table now shows how the number of workers Helen hires is related to the quantity of cookies she produces and to her total cost of production.
In Figure 13.2, compare the total-cost curve in panel (b) with the production function in panel (a). These two curves are opposite sides of the same coin. The total-cost curve gets steeper as the amount produced rises, whereas the production function gets flatter as production rises. These changes in slope occur for the same reason. High production of cookies means that Helen’s kitchen is crowded with many workers. Because the kitchen is crowded, each additional worker adds less to production, reflecting diminishing marginal product. Therefore, the production function is relatively flat. But now turn this logic around: When the kitchen is crowded, producing an additional cookie requires a lot of additional labour and is thus very costly. Therefore, when the quantity produced is large, the total-cost curve is relatively steep.
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If Farmer Jones plants no seeds on his farm, he gets no harvest.
If he plants one bag of seeds, he gets three bushels of wheat.
If he plants two bags, he gets five bushels.
If he plants three bags, he gets six bushels.
A bag of seeds costs $100, and seeds are his only cost.
Use these data to graph the farmer’s production function and total-cost curve.
Explain their shapes.
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20. The Various Measures of Cost
From data on a firm’s total cost, we can derive several related measures of cost, which will turn out to be useful when we analyze production and pricing decisions in future chapters.
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TABLE 13.2: The Various Measures of Cost: Thirsty Thelma’s Lemonade Stand
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22. Fixed and Variable Costs
Fixed costs: costs that do not vary with the quantity of output produced
Variable costs: costs that do vary with the quantity of output produced.
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23. FIGURE 13.3: Thirsty Thelma’s Total-Cost Curve
Here the quantity of output produced (on the horizontal axis) is from the first column in Table 13.2, and the total cost (on the vertical axis) is from the second column. As in panel (b) of Figure 13.2, the total-cost curve gets steeper as the quantity of output increases because of diminishing marginal product.
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24. Fixed and Variable Costs
Fixed costs: costs that do not vary with the quantity of output produced
Variable costs: costs that do vary with the quantity of output produced
A firm’s total cost is the sum of fixed and variable costs.
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25. Average and Marginal Costs
As the owner of her firm, Thelma has to decide how much to produce.
Thelma might ask her production supervisor the following two questions about the cost of producing lemonade:
How much does it cost to make the typical glass of lemonade?
How much does it cost to increase production of lemonade by one glass?
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26. Average and Marginal Costs
Average total cost (ATC): total cost divided by the quantity of output
Average fixed cost (AFC): fixed costs divided by the quantity of output
Average variable cost (AVC): variable costs divided by the quantity of output
Marginal cost (MC): the increase in total cost that arises from an extra unit of production
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27. Average and Marginal Costs
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Active Learning Calculating Costs
Fill in the blank spaces of this table. Q VC TC
AFC
AVC
ATC MC
$50
n/a
n/a
n/a
$10 1 10
$10
$60.00 2 30 80 30 3
16.67 20
36.67 4
100
150
12.50
37.50 5
150 30 60 6
210
260
8.33 35
43.33
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Active Learning Answers
First, deduce FC = $50 and use FC + VC = TC.
Use relationship between MC and TC
Use AVC = VC/Q
Use AFC = FC/Q
Use ATC = TC/Q Q VC TC
AFC
AVC
ATC MC $0
$50
n/a
n/a
n/a
$10 1 10 60
$50.00
$10
$60.00 20 2 30 80
25.00 15
40.00 30 3 60
110
16.67 20
36.67 40 4
100
150
12.50 25
37.50 50 5
150
200
10.00 30
40.00 60 6
210
260
8.33 35
43.33
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30. Cost Curves and Their Shapes
Graphs of average and marginal cost are useful when analyzing the behaviour of firms.
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31. FIGURE 13.4: Thirsty Thelma’s Average-Cost and Marginal-Cost Curves
This figure shows the average total cost (ATC), average fixed cost (AFC), average variable cost (AVC), and marginal cost (MC) for Thirsty Thelma’s Lemonade Stand. All of these curves are obtained by graphing the data in Table These cost curves show three features that are typical of many firms: (1) Marginal cost rises with the quantity of output. (2) The average-total-cost curve is U-shaped. (3) The marginal-cost curve crosses the average-total-cost curve at the minimum of average total cost.
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32. Cost Curves and Their Shapes
Rising Marginal Cost
Thirsty Thelma’s marginal cost rises with the quantity of output produced.
This reflects the property of diminishing marginal product.
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33. Cost Curves and Their Shapes
U-Shaped Average Total Cost
To understand why this is so, remember that average total cost is the sum of average fixed cost and average variable cost.
Average fixed cost always declines as output rises because the fixed cost is spread over a larger number of units.
Average variable cost typically rises as output increases because of diminishing marginal product.
Average total cost reflects the shapes of both average fixed cost and average variable cost. As shown in Figure 13.4, at very low levels of output, such as 1 or 2 glasses of lemonade per hour, average total cost is very high. Even though average variable cost is low, average fixed cost is high because the fixed cost is spread over only a few units. As output increases, the fixed cost is spread more widely. Average fixed cost declines, rapidly at first and then more slowly. As a result, average total cost also declines until Thirsty Thelma’s output reaches 5 glasses of lemonade per hour, when average total cost is $1.30 per glass. When the firm produces more than 6 glasses of lemonade per hour, however, the increase in average variable cost becomes the dominant force, and average total cost starts rising. The tug-of-war between average fixed cost and average variable cost generates the U-shape in average total cost.
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34. Cost Curves and Their Shapes
Efficient scale: the quantity of output that minimizes average total cost
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35. Cost Curves and Their Shapes
The Relationship between Marginal Cost and Average Total Cost
Whenever marginal cost is less than average total cost, average total cost is falling.
Whenever marginal cost is greater than average total cost, average total cost is rising.
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36. FIGURE 13.5: Cost Curves for a Typical Firm
Many firms experience increasing marginal product before diminishing marginal product. As a result, they have cost curves shaped like those in this figure. Notice that marginal cost and average variable cost fall for a while before starting to rise.
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Typical Cost Curves
The cost curves shown here share the three properties that are most important to remember:
Marginal cost eventually rises with the quantity of output.
The average-total-cost curve is U-shaped.
The marginal-cost curve crosses the average-total-cost curve at the minimum of average total cost.
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Suppose Honda’s total cost of producing four cars is $ and its total cost of producing five cars is $
What is the average total cost of producing five cars? What is the marginal cost of the fifth car?
Draw the marginal-cost curve and the average- total-cost curve for a typical firm, and explain why these curves cross where they do.
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39. Costs in the SHORT RUN and In the LONG RUN
We noted earlier in this chapter that a firm’s costs might depend on the time horizon being examined.
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40. FIGURE 13.6: Average Total Cost in the Short and Long Runs
Because fixed costs are variable in the long run, the average-total-cost curve in the short run differs from the average- total-cost curve in the long run.
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41. The Relationship between Short-Run and Long-Run Average Total Cost
For many firms, the division of total costs between fixed and variable costs depends on the time horizon.
Because many decisions are fixed in the short run but variable in the long run, a firm’s long- run cost curves differ from its short-run cost curves.
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42. Economies and Diseconomies of Scale
Economies of scale: the property whereby long-run average total cost falls as the quantity of output increases
Diseconomies of scale: the property whereby long- run average total cost rises as the quantity of output increases
Constant returns to scale: the property whereby long-run average total cost stays the same as the quantity of output changes
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If Bombardier produces nine jets per month, its long-run total cost is $9.0 million per month.
If it produces ten jets per month, its long-run total cost is $9.5 million per month.
Does Bombardier exhibit economies or diseconomies of scale?
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44. TABLE 13.3: The Many Types of Cost: A Summary
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Classroom Activity
Intensive Production
I am interested in growing wheat on a very small plot of land, a plot the size of an average dorm room.
The amount of land is fixed, but any other factors can be added to increase production.
The current method of production involves throwing seeds on the land and returning months later to harvest the grain.
List techniques and inputs that could be used to maximize production from this plot.
Activity 2 Intensive Production
Type: In-class activity
Topics: Marginal cost
Materials needed: None
Time: 5 minutes
Class limitations: Works in any size class
Purpose: This example illustrates how fixed factors cause short-run costs to increase as output increases. Using an agricultural example with a very tight constraint helps make the idea clear.
Instructions: Explain to the class that you are interested in growing wheat on a very small plot of land, a plot the size of an average dorm room. This amount of land is fixed, but any other factors can be added to increase production. The current method of production involves throwing seeds on the land and returning months later to harvest the grain. Ask the students to list techniques and inputs that could be used to maximize production from this plot. Graph the relation between output and marginal cost.
Common Answers: plant more seed; cultivate; fertilize; use herbicide; irrigate; transplant seedlings; use a greenhouse; heat the greenhouse; add high-intensity grow lights in the greenhouse
Points for Discussion: Increasing production by adding more and more inputs increases the marginal costs of production. Extra wheat can be produced from this small plot only at higher cost per bushel.
Purpose: This quick exercise uses an analogy to illustrate to students that they already know the relation between marginal values and averages. The maximum production possible on a given amount of land is far greater than first imagined. Professor Julian Simon (1932−1998) argues a family could produce enough food to feed itself for a year in a bedroom using stacked hydroponics beds. Of course this maximum production goes far beyond the economically optimal use of inputs. This can be used to introduce elements of profit maximization. We don’t grow wheat in greenhouses because the price of wheat is too low to cover the cost. If the value of the product is high enough, any of these agricultural methods could be profitably employed. Commercial greenhouses produce high-priced products like tomatoes and specialty lettuces.
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The end
Chapter 13
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