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By the end of this section, you will be able to:

  • Identify factors that affect demand
  • Graph demand curves and demand shifts
  • Identify factors that affect supply
  • Graph supply curves and supply shifts

The previous module explored how price    affects the quantity demanded and the quantity supplied. The result was the demand curve and the supply curve. Price, however, is not the only thing that influences demand. Nor is it the only thing that influences supply. For example, how is demand for vegetarian food affected if, say, health concerns cause more consumers to avoid eating meat? Or how is the supply of diamonds affected if diamond producers discover several new diamond mines? What are the major factors, in addition to the price, that influence demand or supply?

Visit this website to read a brief note on how marketing strategies can influence supply and demand of products.

What factors affect demand?

We defined demand as the amount of some product a consumer is willing and able to purchase at each price. That suggests at least two factors in addition to price that affect demand. Willingness to purchase suggests a desire, based on what economists call tastes and preferences. If you neither need nor want something, you will not buy it. Ability to purchase suggests that income is important. Professors are usually able to afford better housing and transportation than students, because they have more income. Prices of related goods can affect demand also. If you need a new car, the price of a Honda may affect your demand for a Ford. Finally, the size or composition of the population can affect demand. The more children a family has, the greater their demand for clothing. The more driving-age children a family has, the greater their demand for car insurance, and the less for diapers and baby formula.

These factors matter both for demand by an individual and demand by the market as a whole. Exactly how do these various factors affect demand, and how do we show the effects graphically? To answer those questions, we need the ceteris paribus assumption.

The Ceteris Paribus Assumption

A demand curve    or a supply curve    is a relationship between two, and only two, variables: quantity on the horizontal axis and price on the vertical axis. The assumption behind a demand curve or a supply curve is that no relevant economic factors, other than the product’s price, are changing. Economists call this assumption ceteris paribus    , a Latin phrase meaning “other things being equal.” Any given demand or supply curve is based on the ceteris paribus assumption that all else is held equal. A demand curve or a supply curve is a relationship between two, and only two, variables when all other variables are kept constant. If all else is not held equal, then the laws of supply and demand will not necessarily hold, as the following Clear It Up feature shows.

When does ceteris paribus Apply?

Ceteris paribus is typically applied when we look at how changes in price affect demand or supply, but ceteris paribus can be applied more generally. In the real world, demand and supply depend on more factors than just price. For example, a consumer’s demand depends on income and a producer’s supply depends on the cost of producing the product. How can we analyze the effect on demand or supply if multiple factors are changing at the same time—say price rises and income falls? The answer is that we examine the changes one at a time, assuming the other factors are held constant.

For example, we can say that an increase in the price reduces the amount consumers will buy (assuming income, and anything else that affects demand, is unchanged). Additionally, a decrease in income reduces the amount consumers can afford to buy (assuming price, and anything else that affects demand, is unchanged). This is what the ceteris paribus assumption really means. In this particular case, after we analyze each factor separately, we can combine the results. The amount consumers buy falls for two reasons: first because of the higher price and second because of the lower income.

Questions & Answers

Why is normal indifference curve convex to the origin? In which way does this convexity affect the marginal rate of substitution?
Alwyn Reply
What is Budget constraint
Veena Reply
Budget constraints is when government expenditure is greater than government revenue or when revenue is less than expenditure.
Jeremiah
thanks
fuh
join you to microeconomic
fuh
what is the deferent between quantity demand and quantity demanded
Affoh
what will happen to the budget constraints if the consumer income decline?
Maryam Reply
please what is the relationship between microeconomics and macroeconomics?
Maryam
Accordingly, Microeconomics focuses on the drivers of decision making, as well as the ways in which individuals' decisions affect the overall supply and demand and supply of particular goods and services, in an economy, and in turn their prices. Whereas Macroeconomics is the study of the big picture
Donia
Of the economy (retrieved from Google)
Donia
***quora.com/How-do-microeconomics-and-macroeconomics-interrelate
Donia
when consumer's income decline then purchasing power of consumer decreases .Budget line shifts inward.
Zeeshan
what is a deductive reasoning
tobi Reply
Deductive reasoning makes use of to arrive at the conclusion.That is, the premise must be real and put to rest .
Jeremiah
Deductive statement makes use of facts to arrive at the conclusion.That is ,the premise must be real and put to rest in order to produce the required results.
Jeremiah
what is scarcity
Agegnehu
scarcity is as a result of miss management and poor allocation of resources.
Jeremiah
what is monopoly in economics
Kenneth
price change in case of an inferior good
divya Reply
Search on Google
Harsh
the purchase of an inferior good decreases with increase in income and vice versa
Alwyn
what is frontier
Ebrima Reply
I want the answers
Gideon
What is the difference between microeconomics and macroeconomics?
Krysstel Reply
what is demand
Chidex Reply
demand Is the quantity of goods a consumer is willing and able to produce at a given price and at a particular period of time.
inioluwa
fixed and variable factors of production
muqtaar Reply
James' income declines, and as a result, he buys more spinach. Is spinach an inferior or a normal good? What happens to James' demand curve for spinach?
Alwyn Reply
When the price floor is implemented, the equilibrium quantity will decrease. Is it true or wrong?
naim Reply
it's true
Nathaniel
what is elasticity
Chibuzor Reply
calculate the price elasticity of demand for Mr chibuzor (y) using both arc and price elasticity formulae
Chibuzor
The best way to understand elasticity is just looking to your behavior as a consumer. Just think about the basic need like food. We all know without, one end up dying if could not eat for a couple of days. It is a reason we say the demand is inelastic. It's impossible to survive without food.
busywork
On the other hand, the demand for luxury goods is elastic because it's sensitive to price changes as it is possible to survive without such good like expensive car. We say demand for such goods is elastic because as consumers, we have an option of not buying as it's possible to survive without them.
busywork
pls how do u calculate for the opportunity cost of two commodities when giving two commodities in question, and one is measured in tons and the other is measured in units
DBA Reply
what are tge factors that causes change in demand
emy Reply
change in income change in price change in taste and preference
Wahida
Change in price, ,availability of substitutes ,change in consumer preferences, changes in economic situation.
busywork
Qd=f(Y, P ,Ps ,F, T ,W , Pop)
Zeeshan
substitute goods taste preference income
Hermina
income increase and decrease is the most important reason of demand changing
Taufiq
Price variable : price This leads to a same direction change for certain luxury goods, and to an opposite direction change for the ordinary, normal, inferior... that's the remaining types of goods. As a result, the is a movement along the demand curve. We also have non price variables like income,
Jonas
We also have non price variables like income, that increases the willingness to pay of the consumers and thus increase the demande at any price, leading to a shift of the demand curve to the right if income increases or to the left of income decreases. A change in income also leads to
Jonas
A same direction change in demand for the normal good and for the opposite direction change for inferior goods.
Jonas
We also have other non price variables like taste, time horizon,...
Jonas
what are the production function
Mohammed Reply
capital and land and labor that is called the function production
Mustafe
production is a function of capital and labor.
Zeeshan
land labor capital are the function of production
Mumin
yes
Mustafe
when we existing economic we classify in this action
Mustafe
the technical relationship b/w input and output
Neha
Neha can we say it is not technical relationship
Waseem
How u can say like that Waseem ji
Neha
as far I know it is physical and technical relationship because producer are rational
Neha
so they use physical inputs to get physical output by technical process
Neha
how to use price elasticity of demand for analysis water demand?
Pupu
The production function is the relation between inputs and outputs. It shows how a producer combines the sets of available inputs and resources to maximise his output and thus his turnover.
Jonas
What is indifference curve
JUMA
the are use price to get quality of good and service
Adamu

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Source:  OpenStax, Microeconomics. OpenStax CNX. Aug 03, 2014 Download for free at http://legacy.cnx.org/content/col11627/1.10
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