The change in the ________ of a good leads to a change in ________, which leads to a ________.

What Is Quantity Demanded?

Quantity demanded is a term used in economics to describe the total amount of a good or service that consumers demand over a given interval of time. It depends on the price of a good or service in a marketplace, regardless of whether that market is in equilibrium.

The relationship between the quantity demanded and the price is known as the demand curve, or simply the demand. The degree to which the quantity demanded changes with respect to price is called the elasticity of demand.

Key Takeaways

• In economics, quantity demanded refers to the total amount of a good or service that consumers demand over a given period of time.
• Quantity demanded depends on the price of a good or service in a marketplace.
• The price of a product and the quantity demand for that product have an inverse relationship, according to the law of demand.

Quantity Demanded

Understanding Quantity Demanded

Inverse Relationship of Price and Demand

The price of a good or service in a marketplace determines the quantity that consumers demand. Assuming that non-price factors are removed from the equation, a higher price results in a lower quantity demanded and a lower price results in higher quantity demanded. Thus, the price of a product and the quantity demanded for that product have an inverse relationship, as stated in the law of demand.

An inverse relationship means that higher prices result in lower quantity demand and lower prices result in higher quantity demand.

Change in Quantity Demanded

A change in quantity demanded refers to a change in the specific quantity of a product that buyers are willing and able to buy. This change in quantity demanded is caused by a change in the price.

Increase in Quantity Demanded

An increase in quantity demanded is caused by a decrease in the price of the product (and vice versa). A demand curve illustrates the quantity demanded and any price offered on the market. A change in quantity demanded is represented as a movement along a demand curve. The proportion that quantity demanded changes relative to a change in price is known as the elasticity of demand and is related to the slope of the demand curve.

An Example of Quantity Demanded

Say, for example, at the price of $5 per hot dog, consumers buy two hot dogs per day; the quantity demanded is two. If vendors decide to increase the price of a hot dog to $6, then consumers only purchase one hot dog per day. On a graph, the quantity demanded moves leftward from two to one when the price rises from $5 to $6. If, however, the price of a hot dog decreases to $4, then customers want to consume three hot dogs: the quantity demanded moves rightward from two to three when the price falls from $5 to $4. 

By graphing these combinations of price and quantity demanded, we can construct a demand curve connecting the three points.

Using a standard demand curve, each combination of price and quantity demanded is depicted as a point on the downward sloping line, with the price of hot dogs on the y-axis and the quantity of hot dogs on the x-axis. This means that as price decreases, the quantity demanded increases. Any change or movement to quantity demanded is involved as a movement of the point along the demand curve and not a shift in the demand curve itself. As long as consumers' preferences and other factors don't change, the demand curve effectively remains static.

Price changes change the quantity demanded; changes in consumer preferences change the demand curve. If, for example, environmentally conscious consumers switch from gas cars to electric cars, the demand curve for traditional cars would inherently shift.

Price Elasticity of Demand

The proportion to which the quantity demanded changes with respect to price is called elasticity of demand. A good or service that is highly elastic means the quantity demanded varies widely at different price points.

Conversely, a good or service that is inelastic is one with a quantity demanded that remains relatively static at varying price points. An example of an inelastic good is insulin. Regardless of price point, those who need insulin demand it at the same amount.

What Is Change In Supply?

Change in supply refers to a shift, either to the left or right, in the entire price-quantity relationship that defines a supply curve.

Key Takeaways

• Change in supply refers to a shift, either to the left or right, in the entire price-quantity relationship that defines a supply curve.
• Essentially, a change in supply is an increase or decrease in the quantity supplied that is paired with a higher or lower supply price.
• A change in supply can occur as a result of new technologies, such as more efficient or less expensive production processes, or a change in the number of competitors in the market.
• A change in supply is not to be confused with a change in the quantity supplied.

Understanding Change in Supply

A change in supply is an economic term that describes when the suppliers of a given good or service alter production or output. A change in supply can occur as a result of new technologies, such as more efficient or less expensive production processes, or a change in the number of competitors in the market.

A change in supply leads to a shift in the supply curve, which causes an imbalance in the market that is corrected by changing prices and demand. An increase in the change in supply shifts the supply curve to the right, while a decrease in the change in supply shifts the supply curve left. Essentially, there is an increase or decrease in the quantity supplied that is paired with a higher or lower supply price.

A change in supply shouldn't be confused with a change in the quantity supplied. The former causes a shift in the entire supply curve, while the latter results in movement along the existing supply curve.

The general consensus amongst economists is that these are the primary factors that cause a change in supply, which necessitates the shifting of the supply curve:

• Number of sellers
• Expectations of sellers
• Price of raw materials
• Technology
• Other prices

For example, if a new technology reduces the cost of gaming console production for manufacturers, according to the law of supply the output of consoles will increase. With more output in the market, the price of consoles is likely to fall, creating greater demand in the marketplace and higher overall sales of consoles. This technological advancement has caused a change in supply.

Supply and Demand Curves

The effects of changing supply and demand are found by plotting the two variables on a graph. The horizontal X-axis represents quantity and the vertical Y-axis represents price.

The supply and demand curves intersect to form an "X" in the middle of the graph; the supply curve points upward and to the right, while the demand curve points downward and to the right. Where the two curves intersect is the price and quantity, based on current levels of supply and demand.

A positive change in supply when demand is constant shifts the supply curve to the right, which results in an intersection that yields lower prices and higher quantity. A negative change in supply, on the other hand, shifts the curve to the left, causing prices to rise and the quantity to decrease.

Change in Supply Example

During the early 2010s, the development of hydraulic fracturing, or "fracking", as a method to extract oil from shale rock formations in North America caused a positive change in supply in the oil market. Non-OPEC oil production rose by over one million barrels per day, with most of the oil coming from fracking activity in North America.

Because of the increase in the supply of oil, the per-barrel price of oil, which had reached an all-time high of $147 in 2008, plunged as low as $27 in Feb. 2016. Economists predicted that lower prices would create greater demand for oil, although this demand was tempered by deteriorating economic conditions in many parts of the world.

Does a change in the price of a good lead to a movement along the supply curve or to shift of the supply curve?

What are the causes of change in supply?

When the of a good changes the quantity demanded changes?

Which of the following causes a change in demand?