What happens to equilibrium price and quantity when supply and demand increases?

Supply and Demand is an economic model of price determination in a market. It concludes that in a competitive market, the unit price for a particular good will vary until it settles at a point where the quantity demanded by consumers will equal the quantity supplied by producers resulting in an economic equilibrium of price and quantity. This relationship between supply and demand can be seen in a plot of the classic supply-demand curve on the right. [1]

Definition: The law of supply and demand is a theory that explains the interaction between the sellers of a resource and the buyers for that resource.

What happens to equilibrium price and quantity when supply and demand increases?

What are the Supply and Demand Laws?

The Supply and Demand model has two “laws,”: the (1) Law of Demand and the (2) Law of Supply. These laws interact with each other to determine the market price and volume of goods. The key components to the theory are:

Supply and Demand Outcomes

The four (4) basic outcomes of supply and demand are: [3]

  • If demand increases and supply remains unchanged, a shortage occurs, leading to a higher equilibrium price.
  • If demand decreases and supply remains unchanged, a surplus occurs, leading to a lower equilibrium price.
  • If demand remains unchanged and supply increases, a surplus occurs, leading to a lower equilibrium price.
  • If demand remains unchanged and supply decreases, a shortage occurs, leading to a higher equilibrium price.

(1) What is the Law of Demand?

The Law of Demand refers to the number of products people are willing to buy at different prices at a specific time. The law states that the higher the product price, the fewer people will demand the product.  As a consumer, the higher a product costs, the less the amount of the product the consumer will purchase. This means the opportunity cost of buying that product goes down. [2]

Factors that influence the supply are:

  • Consumer Preference
  • Influence
  • Number of Sellers
  • Taxes and Regulations

(2) What is the Law of Supply?

Supply refers to the quantities of product manufacturers or owners are willing to sell at different prices at a specific time.  The higher the price will result in the higher quantity supplied. As a seller, the opportunity cost of each product is higher, so they want to sell more, and producers want to produce more. [1]

Factors that influence the supply are:

  • Labor and Materials costs
  • Technology availability
  • Number of sellers
  • Capacity
  • Taxes and Regulations

What is Supply and Demand Equilibrium?

The market price is the intersection of the demand price and quantities of products manufactured, and the intersection is called the equilibrium price or Market Clearing Price. The equilibrium price is the price at which the producer can sell all the units he wants to produce, and the buyer can buy all the units he wants.

What happens to equilibrium price and quantity when supply and demand increases?

It is visualized on a chart at the intersection of the supply and demand curve. This intersection is the market price at which suppliers bring to market that same quantity of product that consumers will be willing to buy. They then say the Supply and Demand are in equilibrium.  [1]

Purpose of the Supply and Demand Theory

The purpose of the Supply and Demand theory is to help people, businesses, bankers, investors, entrepreneurs, economists, government, and others understand and predict conditions in the market for best optimization.

Example of the Supply and Demand Theory

What Is an Example of the Law of Supply and Demand?

A bread company wants to introduce a new french bread to its market at the best possible price. To ensure the lowest production price, the manufacturer gets bids from many suppliers to obtain the lowest possible price for manufacturing the new bread.  The lower the cost of the bread, the more profit the company can make if it determines the best price that sells the most quantity of bread. The equilibrium (Market Price) between the quantity of bread sold and the price should bring the most profit.

  • [1] Nickels and McHugh, “Understanding Business” McGraw-Hill Irwin 2010
  • Price Theory – Supply and Demand Lecture  

Updated: 8/9/2022

Rank: G17.5

Video transcript

- [Instructor] What we're going to do in this video is think about all of the different ways that a supply curve or a demand curve can shift and that's why we actually have eight versions of the exact same diagram. Each of them is showing where we are right now, let's say in a given region in the ice cream market. It's important to title your graphs, especially if you were taking some type of a standardized exam like an AP exam and in the vertical axis we have P representing price, and then the horizontal axis, Q representing quantity, we have our upwards sloping supply curve. I'm calling this S1 just as kind of our starting point and then we have our downwards sloping demand curve, D1 and where they intersect, that gives us our equilibrium price, P1 and our equilibrium quantity, Q1 and once again, if you were taking some type of a standardized test, it's important that you label all of these things including P1 and Q1 and show this dotted line where it intersects the horizontal axis, this is Q1 and where it intersects the vertical axis, it is P1. Now with that out of the way, let's think about what happens to the equilibrium price and the equilibrium quantity given different shifts in the supply or the demand curve or both of them. So, in this first scenario, let's imagine that all of a sudden a major ice cream producer enters into the market, so here we're going to this first one, we're gonna think about a situation where the supply goes up. So, one way to think about it is at any given price, people are willing to supply more quantity, so here we would have our supply curve shift to the right, I'll call this S2 right over here, it's shifting to the right and down and so, given this, what happens to our equilibrium price and our equilibrium quantity? Well, you see it right over here. If I draw a dotted line, we see our equilibrium price P2 is lower and our equilibrium quantity Q2 is higher, once again, assuming that we have a downwards sloping demand curve like this which is what you would typically see and so, in this case, let me just write it here, we have our quantity, actually, let me write it this way, we have our price goes down and our quantity goes up. All right, now let's do this example and let's imagine the other way, let's imagine in this scenario our supply goes down. What is going to happen to this graph and in particular, what's going to happen to our equilibrium price and our equilibrium quantity? Well, in this situation for a given price people are willing to supply less, that's how I would like to think about it, so we would have a shift to the left and up and so, we could call this supply curve two right over here and that what is our equilibrium point? It's right over there and so, this would be our new price, it has gone up and this would be our new quantity, it has gone down, so price has gone up and quantity has gone down and once again, in either of these scenarios hopefully this feels a little bit like commonsense. If you have a supplier enter into the market, quantity might go up and there's more competition and so, a lot more suppliers and so, the price would go down. Here where the supply goes down, maybe some of the ice cream stores close down, well, now the quantity will go down, there's just less people supplying but the price goes up. For the ice cream that's there, the equilibrium price is going to be higher. Now let's do the same thing with the demand curve. Let's think about a situation where first let's think about a scenario where demand goes up. What is going to happen in this world? Well, demand might go up because maybe there's some type of report that ice cream is much healthier for you than expected and so, at a given price, people are willing to demand a higher quantity, so for example, at that price, people would demand a higher quantity and so, we would have a shift to the right and up, let's call this D2 right over here and this is our new equilibrium point and then notice what has just happened here. At our new equilibrium point, this is Q2 and then this right over here is P2, our new equilibrium price or our new equilibrium quantity. In this situation where demand goes up, both price and quantity are going to go up assuming we have this upwards sloping supply curve again. And once again, that makes sense. More people just wanna buy ice cream, the supply curve dynamics have not changed, so we're gonna move along that supply curve to the right and up, so both price and quantity go up. Well, if demand goes down, you could imagine the opposite is going to happen. So, here if we have demand goes down, let's say a big study comes out that ice cream is even unhealthier than we originally thought, well, then at a given price, people are going to want, they're going to demand less ice cream and so, our demand curve would shift to the left and down, so we'll call this D2 right over here and then we can see our equilibrium price and quantity, so let's show that new equilibrium price is P2 right over here and then our new equilibrium quantity is Q2 and notice, both price and quantity go down. People just don't wanna buy ice cream as much because they think it's unhealthy now, so price goes down and quantity goes down.

What happens to equilibrium price when supply and demand both increase?

If both demand and supply increase, there will be an increase in the equilibrium output, but the effect on price cannot be determined.

What happens to equilibrium price and quantity when demand increases and supply decreases?

If the increase in demand is more than the decrease in supply, the equilibrium quantity increases. If the increase in demand is less than the decrease in supply, the equilibrium quantity decreases. In both cases, equilibrium price increases.

What happens to quantity when supply and demand increase?

Demand Increase: price increases, quantity increases. Demand Decrease: price decreases, quantity decreases. Supply Increase: price decreases, quantity increases. Supply Decrease: price increases, quantity decreases.

How does equilibrium price and equilibrium quantity when demand and supply increase simultaneously?

"If the demand and supply of a commodity both increase, the equilibrium price may not change, may increase, may decrease."