ECON 1000 Chapter Notes - Chapter 13: Average Cost, Average Variable Cost, Marginal Cost
ECON 1000
CHAPTER 12: THE COSTS OF PRODUCTION
Total revenue, total cost, and profit
Economists normally assume that the goal of a firm is to maximize profit, and they find that this
assumptions works well in most cases.
What is a firī
µās profit? The aī
µouī
¶t that the firī
µ reīeiīes for the sale of its output ī¾īookiesīæ is
called its total revenue. That amount that the firm pays to buy input is called its total cost.
Profit is a firī
µās total reīeī
¶ue ī
µiī
¶us its total īost.
Costs as opportunity costs
Opportunity costs refers to all those things that must be forgone to acquire that item.
Costs can be cost to buy materials, which is money that can no longer be used to purchase
other things or invest elsewhere. When the opportunity costs require the firm to pay out some
ī
µoī
¶eī, theī are īalled eīpliīit īosts ī¾ī
µaterials, īages, etī.īæ. Bī īoī
¶trast, soī
µe of a firī
µās
opportunity costs, called implicit costs, do not require a cash outlay. For example, if you open a
shop, but you could be making 100$ an hour elsewhere, then that would be considered implicit
cost.
Economists use both explicit and implicit costs when measuring total cost. By contrast,
accountants have the job of keeping track of the money that flows into and out of firms.
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. Suppose that Carol used 300K of her savings to
buy her cookie factory. If she had left it in a savings account that pays an interest of 5%, she
would have earned 15K per year. To own her cookie factory, therefore, Carol has given up 15K a
year in interest income.
Economic profit versus accounting profit
An economist measures a firī
µās eīoī
¶oī
µiī profit as the firī
µās total reīeī
¶ue ī
µiī
¶ue all the
opportunity costs (explicit and implicit) of producing the goods and services sold. An
aīīouī
¶taī
¶t ī
µeasures the firī
µās aīīouī
¶tiī
¶g profit as the firī
µās total reīeī
¶ue ī
µiī
¶us oī
¶lī the
firī
µās eīplicit costs. Therefore, accounting profit is usually larger than economic profit.
Economic profit is an important concept because it is what motivates the firms that supply
goods and services.
Production and costs
Firms incur costs when they buy inputs to produce the goods and services they plan to sell.
The production function
The quantity of cookies depends on the number of workers. This is what makes up the
production function (number of workers vs number of cookies)
A total cost curve shows the relationship between the quantity of output produced and total
cost of production.
The marginal product of any input in the production process is the increase in the quantity of
output obtained from one additional unit of that input. When the number of workers goes from
1 to 2, cookie production increases from 50 to 90, so the marginal product of the second
worker is 40 cookies.
As it goes on, we see that the marginal product declines. This is called diminishing marginal
product. At first, when only a few are hired, theī haīe easī aīīess to Carolās kitīheī
¶
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equipment. As the number of workers increases, additional workers have to share equipment
and work in more crowded conditions.
From the production function to the total-cost curve
The total cost curve gets steeper as the amount produced rises, whereas the production
function gets flatter as production rises.
When the quantity produced is large, the total-cost curve is relatively steep.
The various measures of cost
Fixed and variable costs
Fixed costs do not vary with the quantity of output produced. They are incurred even if the firm
produces nothing at all (rent).
Variable costs change as the firm alters the quantity of output produced (coffee beans, cups,
milk, sugar).
Average and marginal costs
Total costs divided by the quantity of output is called average total cost. Because total cost is
just the sum of fixed and variable costs, average total cost can be expressed as the sum of the
average fixed cost and average variable cost. Average fixed cost is the fixed cost divided by the
quantity of output and average variable cost is the variable cost divided by the quantity of
output.
Marginal cost is the amount that total cost rises when the firm increases production by 1 unit of
output.
Average total cost= total cost / quantity
ATC= TC/Q
Marginal cost = change in total cost/ change in quantity
MC= āTC / āQ
Cost curves and their shapes
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Document Summary
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