AS: Unit 1 - Demand and Supply curves in a market and the equilibrium

In this post we will learn:

1. The basics of the demand and supply curve
2. How the price mechanism establishes an equilibrium in a market

So this post will mainly be about the very basic demand and supply diagram.

*ASSUMING CETERUS PARABUS*

Firstly the Demand curve (on the right) is downwards sloping. Why?

This because of the Law of Demand which suggests there is an inverse relationship between the price and demand of a good (hence the axes on the diagram)! This basically means as prices fall (P1 to P2) there will be a increase in quantity demanded (Q1 to Q2), similarly as prices rises (P2 to P1) there will be a decrease in quantity demanded (Q2 to Q1).

 

Secondly the Supply curve (on the left) is upwards sloping. Why?

Well surprise; this is because of the Law of Supply! Similarly to the relationship of the demand curve, as prices increase (P1 to P2) there will be an increase in the quantity supplied (Q1 to Q2) and as prices decrease (P2 to P1) there will be a decrease in the quantity supplied (Q2 to Q1).

 

It is actually quite logical, if you think about it. If the price of  a good decreases of course you're more likely to buy it! Similarly if you sold a good and the price of the good increased of course you'd supply more!  

 

The Equilibrium

 

When demand meets supply the equilibrium is established and there is no tendency for change. Price is at 'P1' and quantity is at 'Q1'.

 

 

However when we're not at equilibrium we are at market disequilibrium and supply does not equal demand.

• If price is at 'Ps'
• Suppliers are willing to supply quantity 'Qy'
• However demand is only at 'Qx'
• Thus there is excess supply (more supply than demand) from points 'A' to 'B' (Qx to Qy)
• If price is at 'Pd'
• Suppliers are only willing to supply at 'Qx'
• However demand is at 'Qy'
• Thus there is excess demand (more demand than supply) from points 'C' to 'D' (Qy to Qx)
• If price is at 'P1'
• There is market equilibrium

---

Please leave feedback and any questions. Thank you! xx