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Whatever the firm’s quantity of production, total revenue must exceed total costs if it is to earn a profit. As explored in the chapter Choice in a World of Scarcity , fixed costs are often sunk costs    that cannot be recouped. In thinking about what to do next, sunk costs should typically be ignored, since this spending has already been made and cannot be changed. However, variable costs can be changed, so they convey information about the firm’s ability to cut costs in the present and the extent to which costs will increase if production rises.

Why are total cost and average cost not on the same graph?

Total cost, fixed cost, and variable cost each reflect different aspects of the cost of production over the entire quantity of output being produced. These costs are measured in dollars. In contrast, marginal cost, average cost, and average variable cost are costs per unit. In the previous example, they are measured as cost per haircut. Thus, it would not make sense to put all of these numbers on the same graph, since they are measured in different units ($ versus $ per unit of output).

It would be as if the vertical axis measured two different things. In addition, as a practical matter, if they were on the same graph, the lines for marginal cost, average cost, and average variable cost would appear almost flat against the horizontal axis, compared to the values for total cost, fixed cost, and variable cost. Using the figures from the previous example, the total cost of producing 40 haircuts is $320. But the average cost is $320/40, or $8. If you graphed both total and average cost on the same axes, the average cost would hardly show.

Average cost tells a firm whether it can earn profits given the current price in the market. If we divide profit by the quantity of output produced we get average profit    , also known as the firm’s profit margin . Expanding the equation for profit gives:

average profit = profit quantity produced = total revenue – total cost quantity produced = total revenue quantity produced total cost quantity produced = average revenue – average cost

But note that:

average revenue = price × quantity produced quantity produced = price

Thus:

average profit = price – average cost

This is the firm’s profit margin . This definition implies that if the market price is above average cost, average profit, and thus total profit, will be positive; if price is below average cost, then profits will be negative.

The marginal cost of producing an additional unit can be compared with the marginal revenue gained by selling that additional unit to reveal whether the additional unit is adding to total profit—or not. Thus, marginal cost helps producers understand how profits would be affected by increasing or decreasing production.

A variety of cost patterns

The pattern of costs varies among industries and even among firms in the same industry. Some businesses have high fixed costs, but low marginal costs. Consider, for example, an Internet company that provides medical advice to customers. Such a company might be paid by consumers directly, or perhaps hospitals or healthcare practices might subscribe on behalf of their patients. Setting up the website, collecting the information, writing the content, and buying or leasing the computer space to handle the web traffic are all fixed costs that must be undertaken before the site can work. However, when the website is up and running, it can provide a high quantity of service with relatively low variable costs, like the cost of monitoring the system and updating the information. In this case, the total cost curve might start at a high level, because of the high fixed costs, but then might appear close to flat, up to a large quantity of output, reflecting the low variable costs of operation. If the website is popular, however, a large rise in the number of visitors will overwhelm the website, and increasing output further could require a purchase of additional computer space.

For other firms, fixed costs may be relatively low. For example, consider firms that rake leaves in the fall or shovel snow off sidewalks and driveways in the winter. For fixed costs, such firms may need little more than a car to transport workers to homes of customers and some rakes and shovels. Still other firms may find that diminishing marginal returns set in quite sharply. If a manufacturing plant tried to run 24 hours a day, seven days a week, little time remains for routine maintenance of the equipment, and marginal costs can increase dramatically as the firm struggles to repair and replace overworked equipment.

Every firm can gain insight into its task of earning profits by dividing its total costs into fixed and variable costs, and then using these calculations as a basis for average total cost, average variable cost, and marginal cost. However, making a final decision about the profit-maximizing quantity to produce and the price to charge will require combining these perspectives on cost with an analysis of sales and revenue, which in turn requires looking at the market structure in which the firm finds itself. Before we turn to the analysis of market structure in other chapters, we will analyze the firm’s cost structure from a long-run perspective.

Key concepts and summary

In a short-run perspective, a firm’s total costs can be divided into fixed costs, which a firm must incur before producing any output, and variable costs, which the firm incurs in the act of producing. Fixed costs are sunk costs; that is, because they are in the past and cannot be altered, they should play no role in economic decisions about future production or pricing. Variable costs typically show diminishing marginal returns, so that the marginal cost of producing higher levels of output rises.

Marginal cost is calculated by taking the change in total cost (or the change in variable cost, which will be the same thing) and dividing it by the change in output, for each possible change in output. Marginal costs are typically rising. A firm can compare marginal cost to the additional revenue it gains from selling another unit to find out whether its marginal unit is adding to profit.

Average total cost is calculated by taking total cost and dividing by total output at each different level of output. Average costs are typically U-shaped on a graph. If a firm’s average cost of production is lower than the market price, a firm will be earning profits.

Average variable cost is calculated by taking variable cost and dividing by the total output at each level of output. Average variable costs are typically U-shaped. If a firm’s average variable cost of production is lower than the market price, then the firm would be earning profits if fixed costs are left out of the picture.

Problems

Return to [link] . What is the marginal gain in output from increasing the number of barbers from 4 to 5 and from 5 to 6? Does it continue the pattern of diminishing marginal returns?

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Compute the average total cost, average variable cost, and marginal cost of producing 60 and 72 haircuts. Draw the graph of the three curves between 60 and 72 haircuts.

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Questions & Answers

what are the importance of studying Economics ?
Amoako Reply
what is monopoly
Baku Reply
is a structure where one seller of a commodity has no close substitute with very many buyers
rivan
tanx
Baku
a market structure where a particular good has no close substitutes
Koushik
examples railways
Shashank
what is income elasticity of demand.
kwagala Reply
percentage change in quantity demanded/percentage change in income
Koushik
or is the measure of degree of responsiveness o quality demanded o the commodity to change in the income of consumer
rivan
percentage change in quantity ÷ percentage change in income
Baku
what is medium
Chinedu Reply
what is medium in terms of economics
Chinedu
as u mean medium of exchange or just as a word
rivan
Your question is not clear @Chinedu. In economics medium is often used in relation to time e.g medium term. So you need to be more specific on which medium you mean. Otherwise it "medium" means what it means everywhere else.
elizabeth
What is the difference between inferior goods and complementary goods
Bernard Reply
inferior goods are goods whose demand reduces as consumers income increases
rivan
while complementary goods are goods which are jointly demand
rivan
Wow thanks
Bernard
you are welcome
rivan
define the term derived demand
rivan Reply
anyone to help with QN
rivan
situation in which a product is acquired not for it's sake but to help in the production of other goods. for example we say labour has a derived demand becos labour services is required to help in the production of other goods and services.
PETER
The Market equilibrium quantity is___ tons of bolts, the socailly optimal quantity of bolt production is ____ tons
Jackie Reply
please what are the key principles of Economics?
Amoako
how to learn about stock exchange market?
jason Reply
how to get to clearly know about BSE and NSE
jason
hiii
santosh
hii
Leela
hlo
Peter
i wanna know about ppf
Peter
Me too
Teremi
Search in web,
Leela
search in website
Leela
Search in web,
Leela
BSE means Bombay stock exchange,and NSE national stock exchange
Leela
What are the uses stastitics in business?
Mohamud Reply
what's scarcity
Brandon Reply
scarcity is the stage at which your end becomes greater than your want.
Caasianebok
refers to limited supply of commodity in relative of their demand
rivan
unlimited wants - limited resources
Brock
what is marginal rate of transformation
Peter Reply
difference between individual demand and market demand with illustrations.
kwagala Reply
what is market demand
kwagala
Is the total amount of goods and services that all consumers are willing and able to purchase...
Istar
market demad business
zahid
What is the different between demand and supply?
Mohamud Reply
Demand is a natural phenomenon by a person who wants a certain commodity , u can say The ablity to buy a certain commodity at a certain price is called demand
Wardan
supply is point of view from Supplier of certain commodity
Wardan
Thnks wardan sheikh
Mohamud
u can get help from Law of Demand which is When a price of certain commodity increases it's quantity demanded decreases and when the price of certain commodity decreases it's quantity demanded increases and vice versa
Wardan
and to understand supply u can understand by the help of law of supply which is when a price of certain commodity increases it's quantity supplies also increases and when price of certain commodity decreases it's quantity supplies also decreases and vice versa
Wardan
Hope u got the answer
Wardan
hi
Christian
hello
Victory
what is point?
Asmatullah
pls it's quantity supplied not quantity supplies. tanx
PETER
Peter it's just typing error if u know better u should take initiatives and start helping people or u can just shut up
Wardan
What is the labour market?
Ruchi
Ruchi Shukla it's a big topic which contains several parts , u can understand a market where there are number of employees (skilled and semiskilled )
Wardan
describe the economic systems
kivumbi
ryt nice
Destiny
what is the cause of a country's population
Destiny
Destiny Abekah the cause Is fun ahahahaha
Wardan
Hi
Crahmaan
What is going here?
Crahmaan
Hi
Jacob
what is naxion shoks any 1 can explain please
Iftikhar
hello
Hydrammeh
impact of transport and communication for economic help me
Jacob
according to me supply is the amount of goods and services that a seller is prepared to offer at a given prior of time while demand is the amount of goods and services that a consumer is enable and willing to pay at a given period of time ..... according to my understanding
rivan
What is the formula for calculating elasticity
Destiny Reply
Change in Quantity/Change in price
Abdul
ok
Destiny
E=%∆ in Q/ %∆ in P
ashafa
what mean elasticity
Jimcaale
change in quantity divided by change in price
mukhtaar
ok
Abdul
price elasticity = Q2-Q1/Q2+Q1/2/ P2-P1/P2+P1/2
Wardan
second formula is change in q / change in p × Q(original)/ p (original)
Wardan
Elasticity is just a measurement of change influenced by change in price , income
Wardan
change quantity /change in price
Ayaan
ok
Muhammad
change in price change in quality
Muhammad
yes
Thomas
calculations are mob eg cross elasticity,relevate n others mob which do u mean
rivan
public economy vs public choice
martha Reply
cool n you
Godwin
nice
Saratu
thank God
Destiny
so wat is going on
Destiny
please understand change in demand.
Saratu
learning is going on please.
Saratu
demand changes when the price of the commodies in the market increaaes
Destiny
amd vise veser
Destiny
thank you.
Saratu
same to u
Destiny

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Source:  OpenStax, Principles of economics. OpenStax CNX. Sep 19, 2014 Download for free at http://legacy.cnx.org/content/col11613/1.11
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