Economics Chapter 4 - Demand

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EconomicsChapter 4
Demand
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Section 2
Shifts of the Demand Curve
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Shifts in Demand

• Ceteris paribus is a Latin phrase economists use
  meaning all other things held constant.
• A demand curve is accurate only as long as the
  ceteris paribus assumption is true.
• When the ceteris paribus assumption is dropped,
  movement no longer occurs along the demand curve.
  Rather, the entire demand curve shifts.

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In the example using pizza sales in the Section
1, the demand schedules and curves would seem to
furnish all the information.
Other factors, however, might also have an effect
on the marketing of pizza.
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In the example only the price of pizza is the
variable. In reality there are other variables.
For instance, what if the government published an
article saying that testing shows that tomato
sauce has a very strong chemical that increases
human life.
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If menus had already been printed or ingredients
have already been purchased, this news would have
changed the decisions made for pizza production.
The news probably means that more pizza will be
sold and it would command a higher price.
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The demand curve is accurate as long as there are
no changes other than price.
In other words, the demand curve is only accurate
as long as the ceteris paribus assumption holds.
When this is true, a change in price of pizza
involves a shift to a different quantity of pizza.
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When the ceteris paribus rule is dropped and
allow other factors to change, the move is no
longer on the demand curve.
This shift in the demand curve means that at
every price, the consumers buy a different
quantity of pizza.
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As an example, if the town had a heat wave and no
one was hungry for pizza, fewer slices would be
sold at every price.
This is called a change in demand and yields a
shift in
the demand curve.
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What Causes a Shift in Demand?

• Several factors can lead to a change in demand

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• 1. Income
• Changes in consumers incomes affect demand.
• A normal good is a good that consumers demand
  more of when their incomes increase.
• An inferior good is a good that consumers demand
  less of when their income increases.

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• 2. Consumer Expectations
• Whether or not we expect a good to increase or
  decrease in price in the future greatly affects
  our demand for that good today.

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• 3. Population
• Changes in the size of the population also
  affects the demand for most products.

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• 4. Consumer Tastes and Advertising
• Advertising plays an important role in many
  trends and therefore influences demand.

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Prices of Related Goods

• The demand curve for one good can be affected by
  a change in the demand for another good.

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Complements and Substitutes

• Complements are two goods that are bought and
  used together. Example skis and ski boots,
  peanut butter and jelly
• Substitutes are goods used in place of one
  another. Example skis and snowboards, peanut
  butter and tuna