Economics Basics: Supply and Demand
By Reem Heakal
A. The Law of Demand
The law of demand states that, if all other factors remain equal, the higher the price of a
good, the less people will demand that good. In other words, the higher the price, the lower
the quantity demanded. The amount of a good that buyers purchase at a higher price is less
because as the price of a good goes up, so does the opportunity cost of buying that good.
As a result, people will naturally avoid buying a product that will force them to forgo the
consumption of something else they value more. The chart below shows that the curve is a
downward slope.
A, B and C are points on the demand curve. Each point on the curve reflects a direct
correlation between quantity demanded (Q) and price (P). So, at point A, the quantity
demanded will be Q1 and the price will be P1, and so on. The demand relationship curve
illustrates the negative relationship between price and quantity demanded. The higher the
price of a good the lower the quantity demanded (A), and the lower the price, the more the
good will be in demand (C).
B. The Law of Supply
Like the law of demand, the law of supply demonstrates the quantities that will be sold at a
certain price. But unlike the law of demand, the supply relationship shows an upward slope.
This means that the higher the price, the higher the quantity supplied. Producers supply
more at a higher price because selling a higher quantity at a higher price increases
revenue.
A, B and C are points on the supply curve. Each point on the curve reflects a direct
correlation between quantity supplied (Q) and price (P). At point B, the quantity supplied will
be Q2 and the price will be P2, and so on.
Time and Supply
Unlike the demand relationship, however, the supply relationship is a factor of time. Time is
important to supply because suppliers must, but cannot always, react quickly to a change in
demand or price. So it is important to try and determine whether a price change that is
caused by demand will be temporary or permanent.
Let's say there's a sudden increase in the demand and price for umbrellas in an unexpected
rainy season; suppliers may simply accommodate demand by using their production
equipment more intensively. If, however, there is a climate change, and the population will
need umbrellas year-round, the change in demand and price will be expected to be long
term; suppliers will have to change their equipment and production facilities in order to meet
the long-term levels of demand.
C. Equilibrium
When supply and demand are equal (i.e. when the supply function and demand function
intersect) the economy is said to be at equilibrium. At this point, the allocation of goods is at
its most efficient because the amount of goods being supplied is exactly the same as the
amount of goods being demanded. Thus, everyone (individuals, firms, or countries) is
satisfied with the current economic condition. At the given price, suppliers are selling all the
goods that they have produced and consumers are getting all the goods that they are
demanding.
As you can see on the chart, equilibrium occurs at the intersection of the demand and
supply curve, which indicates no allocative inefficiency. At this point, the price of the goods
will be P* and the quantity will be Q*. These figures are referred to as equilibrium price and
quantity.
In the real market place equilibrium can only ever be reached in theory, so the prices of
goods and services are constantly changing in relation to fluctuations in demand and
supply.
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