A change in the price of pizza would not shift this demand curve; it would only lead to a movement from one point to another along the same demand curve.
Examples of things that would shift the supply curve include changes in prices of inputs like tomato sauce and cheese, changes in technology like more efficient pizza ovens or automatic dough makers, changes in expectations about the future price of a pizza, or a change in the number of sellers. A change in the price of pizza would not shift this supply curve; it would only lead to a movement from one point to another along the same supply curve. If the price of tomatoes rises, the supply curve for pizza shifts to the left because there has been an increase in the price of an input into pizza production, but there is no shift in demand. The shift to the left of the supply curve causes the equilibrium price to rise and the equilibrium quantity to decline. If the price of hamburgers falls, the demand curve for pizza shifts to the left because the lower price of hamburgers will lead consumers to buy more hamburgers and fewer pizzas, but there is no shift in supply.
The shift to the left of the demand curve causes the equilibrium price to fall and the equilibrium quantity to decline.
Questions for Review
- A competitive market is a market in which there are many buyers and many sellers of an identical product so that each has a negligible impact on the market price. Another type of market is a monopoly, in which there is only one seller. There are also other markets that fall between perfect competition and monopoly.
- The demand schedule is a table that shows the relationship between the price of a good and the quantity demanded. The demand curve is the downward-sloping line relating to price and quantity demanded. The demand schedule and demand curve are related because the demand curve is simply a graph showing the points in the demand schedule. The demand curve slopes downward because of the law of demand—other things being equal, when the price of good rises, the quantity demanded of the good falls. People buy less of a good when its price rises, both because they cannot afford to buy as much and because they switch to purchasing other goods.
- A change in consumers’ tastes leads to a shift of the demand curve. A change in price leads to a movement along the demand curve.
- Because Popeye buys more spinach when his income falls, spinach is an inferior good for him. Because he buys more spinach and the price of spinach is unchanged, his demand curve for spinach shifts out as a result of the decrease in his income.
- A supply schedule is a table showing the relationship between the price of a good and the quantity a producer is willing and able to supply. The supply curve is the upward-sloping line relating to price and quantity supplied. The supply schedule and the supply curve are related because the supply curve is simply a graph showing the points in the supply schedule. The supply curve slopes upward because when the price is high, suppliers’ profits increase, so they supply more output to the market. The result is the law of supply—other things being equal, when the price of good rises, the quantity supplied of the good also rises.
- A change in producers’ technology leads to a shift in the supply curve. A change in price leads to a movement along the supply curve.
- The equilibrium of a market is the point at which the quantity demanded is equal to the quantity supplied. If the price is above the equilibrium price, sellers want to sell more than buyers want to buy, so there is a surplus. Sellers try to increase their sales by cutting prices. That continues until they reach the equilibrium price. If the price is below the equilibrium price, buyers want to buy more than sellers want to sell, so there is a shortage. Sellers can raise their prices without losing customers. That continues until they reach the equilibrium price.
- When the price of beer rises, the demand for pizza declines, because beer and pizza are compliments and people want to buy less beer. When we say the demand for pizza declines, we mean that the demand curve for pizza shifts to the left. The supply curve for pizza is not affected. With a shift to the left in the demand curve, the equilibrium price and quantity both decline. Thus, the quantity of pizza supplied and demanded both falls. In sum, supply is unchanged, demand is decreased, quantity supplied declines, quantity demanded declines, and the price falls.
- Prices play a vital role in market economies because they bring markets into equilibrium. If the price is different from its equilibrium level, the quantity supplied and quantity demanded are not equal. The resulting surplus or shortage leads suppliers to adjust the price until equilibrium is restored. Prices thus serve as signals that guide economic decisions and allocate scarce resources.
Problems and Applications
Cold weather damages the orange crop, reducing the supply of oranges. This can be seen as a shift to the left in the supply curve for oranges.
The new equilibrium price is higher than the old equilibrium price.
People often travel to the Caribbean from New England to escape cold weather, so the demand for Caribbean hotel rooms is high in the winter. In the summer, fewer people travel to the Caribbean, because northern climes are more pleasant. The result is a shift to the left in the demand curve. The equilibrium price of Caribbean hotel rooms is thus lower in the summer than in the winter.
When a war breaks out in the Middle East, many markets are affected. Because a large proportion of oil production takes place there, the war disrupts oil supplies, shifting the supply curve for gasoline to the left. The result is a rise in the equilibrium price of gasoline. With a higher price for gasoline, the cost of operating a gas-guzzling automobile like a Cadillac will increase. As a result, the demand for used Cadillacs will decline, as people in the market for cars will not find Cadillacs as attractive. In addition, some people who already own Cadillacs will try to sell them.
The result is that the demand curve for used Cadillacs shifts to the left, while the supply curve shifts to the right. The result is a decline in the equilibrium price of used Cadillacs. The statement that “an increase in the demand for notebooks raises the number of notebooks demanded, but not the quantity supplied,” in general, is false. The increases in demand for notebooks results in an increased quantity supplied. The only way the statement would be true is if the supply curve was a vertical line.
If people decide to have more children, they will want larger vehicles for hauling their kids around, so the demand for minivans will increase. Supply will not be affected. The result is a rise in both the price and the quantity sold. If a strike by steelworkers raises steel prices, the cost of producing a minivan rises, and the supply of minivans decreases. Demand will not be affected. The result is a rise in the price of minivans and a decline in the quantity sold.
The development of new automated machinery for the production of minivans is an improvement in technology. This reduction in firms’ costs will result in an increase in supply. The demand is not affected. The result is a decline in the price of minivans and an increase in the quantity sold. The rise in the price of sport utility vehicles affects minivan demand because sport utility vehicles are substitutes for minivans. The result is an increase in demand for minivans. Supply is not affected. The equilibrium price and quantity of minivans both rise.
The reduction in peoples’ wealth caused by a stock-market crash reduces their income, leading to a reduction in the demand for minivans because minivans are likely a normal good. Supply is not affected. As a result, both the equilibrium price and the equilibrium quantity decline. If the demand for bread falls, the equilibrium price of bread does indeed fall. However, the price decrease causes a rise in the quantity of bread demanded (illustrated by a movement along the new demand curve).
DVDs and TV screens are likely to be complimented because you cannot watch a DVD without a television.
DVDs and movie tickets are likely to be substituted because a movie can be watched at a theater or at home. TV screens and movie tickets are likely to be substituted for the same reason. b. The technological improvement would reduce the cost of producing a TV screen, shifting the supply curve to the right. The demand curve would not be affected. The result is that the equilibrium price will fall, while the equilibrium quantity will rise. The reduction in the price of TV screens would lead to an increase in the demand for DVDs because TV screens and DVDs are complements.
The effect of this increase in the demand for DVDs is an increase in both the equilibrium price and quantity. The reduction in the price of TV screens would cause a decline in the demand for movie tickets because TV screens and movie tickets are substitute goods. The decline in the demand for movie tickets would lead to a decline in the equilibrium price and quantity sold.
Technological advances that reduce the cost of producing computer chips represent a decline in an input price for producing a computer.
The result is a shift to the right in the supply of computers. The equilibrium price falls and the equilibrium quantity rises. Because computer software is a complement to computers, the lower equilibrium price of computers increases the demand for software. The result is a rise in both the equilibrium price and quantity of software. Because typewriters are substitutes for computers, the lower equilibrium price of computers reduces the demand for typewriters.
The result is a decline in both the equilibrium price and quantity of typewriters. When a hurricane in South Carolina damages the cotton crop, it raises input prices for producing sweatshirts. As a result, the supply of sweatshirts shifts to the left. The new equilibrium price is higher and the new equilibrium quantity of sweatshirts is lower. A decline in the price of leather jackets leads more people to buy leather jackets, reducing the demand for sweatshirts. The result is a decline in both the equilibrium price and quantity of sweatshirts.
The effects of colleges requiring students to engage in a morning exercise inappropriate attire raise the demand for sweatshirts. The result is an increase in both the equilibrium price and quantity of sweatshirts. The invention of new knitting machines increases the supply of sweatshirts. The result is a reduction in the equilibrium price and an increase in the equilibrium quantity of sweatshirts.
Reduced police efforts would lead to an increase in the supply of drugs.
This would cause the equilibrium price of drugs to fall and the equilibrium quantity of drugs to rise. On the other hand, cutbacks in education efforts would lead to a rise in the demand for drugs. This would push the equilibrium price and quantity up.
A fall in the equilibrium price would lead us to believe the first hypothesis. If the equilibrium price rose, we would believe the second hypothesis. A temporarily high birth rate in the year 2010 leads to opposite effects on the price of babysitting services in the years 2015 and 2025.
In the year 2015, there are more five-year-olds who need sitters, so the demand for baby-sitting services rises. The result is a higher price for babysitting services in 2015. However, in the year 2025, the increased number of 15-year-olds shifts the supply of babysitting services to the right. The result is a decline in the price of babysitting services.
Ketchup is a complement for hot dogs. Therefore, when the price of hot dogs rises, the quantity demanded of hot dogs falls and this lowers the demand for ketchup.
The end result is that both the equilibrium price and quantity of ketchup fall. Because the quantity of ketchup falls, the demand for tomatoes by ketchup producers falls, so the equilibrium price and quantity of tomatoes fall. When the price of tomato falls, producers of tomato juice face lower input prices, so the supply curve for tomato juice shifts out, causing the price of tomato juice to fall and the quantity of tomato juice to rise. The fall in the price of tomato juice causes people to substitute tomato juice for orange juice, so the demand for orange juice declines, causing the price and quantity of orange juice to fall.
Now you can see clearly why a rise in the price of hot dogs leads to a fall in the price of orange juice!
Quantity supplied equals quantity demanded at a price of $6 and a quantity of 81 pizzas. If the price were greater than $6, the quantity supplied would exceed the quantity demanded, so suppliers would reduce the price to gain sales. If the price were less than $6, the quantity demanded would exceed the quantity supplied, so suppliers could raise the price without losing sales. In both cases, the price would continue to adjust until it reached $6, the only price at which there is neither a surplus nor a shortage.
The news of the increased health benefits from consuming oranges will increase the demand for oranges, increasing both the equilibrium price and quantity. If farmers use a new fertilizer that makes orange trees more productive, the supply of oranges will increase, leading to a fall in the equilibrium price but a rise in the equilibrium quantity. If both occur at the same time, the equilibrium quantity will definitely rise, but the effect on equilibrium price will be ambiguous.
Because flour is an ingredient in bagels, a decline in the price of flour would shift the supply curve for bagels to the right. The result would be a fall in the price of bagels and a rise in the equilibrium quantity of bagels.
Because cream cheese is a complement to bagels, the fall in the equilibrium price of bagels increases the demand for cream cheese. The result is a rise in both the equilibrium price and quantity of cream cheese. So, a fall in the price of flour indeed raises both the equilibrium price of cream cheese and the equilibrium quantity of bagels.
What happens if the price of milk falls? Because milk is an ingredient in cream cheese, the fall in the price of milk leads to an increase in the supply of cream cheese. This leads to a decrease in the price of cream cheese, rather than a rise in the price of cream cheese. So a fall in the price of milk could not have been responsible for the pattern observed.
In part (a), we found that a fall in the price of flour led to a rise in the price of cream cheese and a rise in the equilibrium quantity of bagels.
If the price of flour rose, the opposite would be true; it would lead to a fall in the price of cream cheese and a fall in the equilibrium quantity of bagels. Because the question says the equilibrium price of cream cheese has risen, it could not have been caused by a rise in the price of flour. What happens if the price of milk rises? From part (a), we found that a fall in the price of milk caused a decline in the price of cream cheese, so a rise in the price of milk would cause a rise in the price of cream cheese.
Because bagels and cream cheese are complements, the rise in the price of cream cheese would reduce the demand for bagels. The result is a decline in the equilibrium quantity of bagels. So a rise in the price of milk does cause both a rise in the price of cream cheese and a decline in the equilibrium quantity of bagels. The supply curve is vertical. The constant quantity supplied makes sense because the basketball arena has a fixed number of seats at any price.
Equilibrium occurs where the quantity demanded is equal to the quantity supplied.
Thus: Qd = Qs 1,600 – 300P = 1,400 + 700P 200 = 1,000P P = $0. 20 Qd = 1,600 – 300(0. 20) = 1,600 – 60 = 1,540 Qs = 1,400 + 700(0. 20) = 1,400 + 140 = 1,540. The equilibrium price of a chocolate bar is $0. 20 and the equilibrium quantity is 1,540 bars.
