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By the end of this section, you will be able to:

  • Identify equilibrium price and quantity through the four-step process
  • Graph equilibrium price and quantity
  • Contrast shifts of demand or supply and movements along a demand or supply curve
  • Graph demand and supply curves, including equilibrium price and quantity, based on real-world examples

Let’s begin this discussion with a single economic event. It might be an event that affects demand, like a change in income, population, tastes, prices of substitutes or complements, or expectations about future prices. It might be an event that affects supply, like a change in natural conditions, input prices, or technology, or government policies that affect production. How does this economic event affect equilibrium price and quantity? We will analyze this question using a four-step process.

Step 1. Draw a demand and supply model before the economic change took place. To establish the model requires four standard pieces of information: The law of demand, which tells us the slope of the demand curve; the law of supply, which gives us the slope of the supply curve; the shift variables for demand; and the shift variables for supply. From this model, find the initial equilibrium values for price and quantity.

Step 2. Decide whether the economic change being analyzed affects demand or supply. In other words, does the event refer to something in the list of demand factors or supply factors?

Step 3. Decide whether the effect on demand or supply causes the curve to shift to the right or to the left, and sketch the new demand or supply curve on the diagram. In other words, does the event increase or decrease the amount consumers want to buy or producers want to sell?

Step 4. Identify the new equilibrium and then compare the original equilibrium price and quantity to the new equilibrium price and quantity.

Let’s consider one example that involves a shift in supply and one that involves a shift in demand. Then we will consider an example where both supply and demand shift.

Good weather for salmon fishing

In the summer of 2000, weather conditions were excellent for commercial salmon fishing off the California coast. Heavy rains meant higher than normal levels of water in the rivers, which helps the salmon to breed. Slightly cooler ocean temperatures stimulated the growth of plankton, the microscopic organisms at the bottom of the ocean food chain, providing everything in the ocean with a hearty food supply. The ocean stayed calm during fishing season, so commercial fishing operations did not lose many days to bad weather. How did these climate conditions affect the quantity and price of salmon? [link] illustrates the four-step approach, which is explained below, to work through this problem. [link] provides the information to work the problem as well.

Good weather for salmon fishing: the four-step process

The graph represents the four-step approach to determining shifts in the new equilibrium price and quantity in response to good weather for salmon fishing.
Unusually good weather leads to changes in the price and quantity of salmon.
Salmon fishing
Price per Pound Quantity Supplied in 1999 Quantity Supplied in 2000 Quantity Demanded
$2.00 80 400 840
$2.25 120 480 680
$2.50 160 550 550
$2.75 200 600 450
$3.00 230 640 350
$3.25 250 670 250
$3.50 270 700 200

Questions & Answers

how to print
Siti Reply
what is flow variable
Siyanda Reply
a flow is a quantity that can be measured over a specific period of time
is economics a social science or a pure science
Hilda Reply
social science
social science
social Science as a Subject and Pure science as a study
How to compute National income by using the expenditure approach
Bridget Reply
explain the method?
C+I+G+(X-M) C= Consumption Expenditure I= Investment Expenditure G= Government Expenditure X-M = Net Export
hw r u..?
am good
o nice
please I need a guardian on this topic
What do you need? Maybe we can help
What's going on here?
l need some information about macroeconomic
First tell us what you already know about macroeconomic.
any lecturer in here?
yes !! am here !! Lecturer of Economics And Statistics
Macroeconomics is too vast,so please be specific your question
Briefly explain whether the discipline of economics is a social science or pure science( normative or positive)
Okafor Reply
answer.... Economics is social science
different between absolute advantage and comparative advantage
mathematical economics
masele Reply
show some questions under this topic
why met worth is added with libilitys in the balance sheet
bijoy Reply
what are the implications of inflation targeting?
Alinaitwe Reply
maximize profit
What happens to the goods and money market if the government cuts public spending?
Harman Reply
then the government will be punished by the public
GDP, INFLATION, UNEMPLOYMENT & PRODUCTIVITY and then write a paragraph on the behavior of each variable after analyzing them graphically.
what is international trade
Stella Reply
International trade is the exchange of capital, goods, and services across international borders.
international trade is the exchange of goods and services across boundaries
international trade is the exchange of goods and services of country and abroad
international is the process of exchanges of value interm of goods and services along national frontier
Increase knowdge and skill. it save time and cost. Increase high Efficiency of production .
betta Reply
List kinds of Elastcity of Demand
Is a faster rate of economic growth always a good thing as compared to a slower rate? And why?
what is unemployment
Doctor Reply
it is a situation during which workers remain jobless.
is situation where people are willing to work but job are no available
what is inflation
Sheila Reply
Inflation is a major concern to global economists, and it affects people from all walks of life. It refers to the measure or rate by which the cost of goods and services rises and purchasing power declines. As prices increase, monetary value decreases—prompting consumers to spend less on goods and s
inflation is the persistence rise in price level
Inflation is the situation during which too much money is required to purchase too few goods.
inflation is continuous increase in general price level
it is the process where too much money pursuing fewer goods

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Source:  OpenStax, Macroeconomics. OpenStax CNX. Jun 16, 2014 Download for free at http://legacy.cnx.org/content/col11626/1.10
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