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

  • Interpret a circular flow diagram
  • Explain the importance of economic theories and models
  • Describe goods and services markets and labor markets

John maynard keynes

The image is a photograph of John Maynard Keynes.
One of the most influential economists in modern times was John Maynard Keynes. (Credit: Wikimedia Commons)

John Maynard Keynes (1883–1946), one of the greatest economists of the twentieth century, pointed out that economics is not just a subject area but also a way of thinking. Keynes, shown in [link] , famously wrote in the introduction to a fellow economist’s book: “[Economics] is a method rather than a doctrine, an apparatus of the mind, a technique of thinking, which helps its possessor to draw correct conclusions.” In other words, economics teaches you how to think, not what to think.

Watch this video about John Maynard Keynes and his influence on economics.

Economists see the world through a different lens than anthropologists, biologists, classicists, or practitioners of any other discipline. They analyze issues and problems with economic theories that are based on particular assumptions about human behavior, that are different than the assumptions an anthropologist or psychologist might use. A theory    is a simplified representation of how two or more variables interact with each other. The purpose of a theory is to take a complex, real-world issue and simplify it down to its essentials. If done well, this enables the analyst to understand the issue and any problems around it. A good theory is simple enough to be understood, while complex enough to capture the key features of the object or situation being studied.

Sometimes economists use the term model    instead of theory. Strictly speaking, a theory is a more abstract representation, while a model is more applied or empirical representation. Models are used to test theories, but for this course we will use the terms interchangeably.

For example, an architect who is planning a major office building will often build a physical model that sits on a tabletop to show how the entire city block will look after the new building is constructed. Companies often build models of their new products, which are more rough and unfinished than the final product will be, but can still demonstrate how the new product will work.

A good model to start with in economics is the circular flow diagram    , which is shown in [link] . It pictures the economy as consisting of two groups—households and firms—that interact in two markets: the goods and services market    in which firms sell and households buy and the labor market    in which households sell labor to business firms or other employees.

The circular flow diagram

The circular flow diagram’s outer arrows represent a goods and services market, and the inner arrows represent a labor market. As illustrated by the outer arrows, in a goods and services market, firms give goods and services to households and, in exchange, households give payment to firms. As illustrated by the inner arrows, in a labor market, households provide labor to firms and, in exchange, firms give wages, salaries, and benefits to households.
The circular flow diagram shows how households and firms interact in the goods and services market, and in the labor market. The direction of the arrows shows that in the goods and services market, households receive goods and services and pay firms for them. In the labor market, households provide labor and receive payment from firms through wages, salaries, and benefits.

Of course, in the real world, there are many different markets for goods and services and markets for many different types of labor. The circular flow diagram simplifies this to make the picture easier to grasp. In the diagram, firms produce goods and services, which they sell to households in return for revenues. This is shown in the outer circle, and represents the two sides of the product market (for example, the market for goods and services) in which households demand and firms supply. Households sell their labor as workers to firms in return for wages, salaries and benefits. This is shown in the inner circle and represents the two sides of the labor market in which households supply and firms demand.

This version of the circular flow model is stripped down to the essentials, but it has enough features to explain how the product and labor markets work in the economy. We could easily add details to this basic model if we wanted to introduce more real-world elements, like financial markets, governments, and interactions with the rest of the globe (imports and exports).

Economists carry a set of theories in their heads like a carpenter carries around a toolkit. When they see an economic issue or problem, they go through the theories they know to see if they can find one that fits. Then they use the theory to derive insights about the issue or problem. In economics, theories are expressed as diagrams, graphs, or even as mathematical equations. (Do not worry. In this course, we will mostly use graphs.) Economists do not figure out the answer to the problem first and then draw the graph to illustrate. Rather, they use the graph of the theory to help them figure out the answer. Although at the introductory level, you can sometimes figure out the right answer without applying a model, if you keep studying economics, before too long you will run into issues and problems that you will need to graph to solve. Both micro and macroeconomics are explained in terms of theories and models. The most well-known theories are probably those of supply and demand, but you will learn a number of others.

Key concepts and summary

Economists analyze problems differently than do other disciplinary experts. The main tools economists use are economic theories or models. A theory is not an illustration of the answer to a problem. Rather, a theory is a tool for determining the answer.

Questions & Answers

this means that the demand curve have negative relationship with the price ..which means that when high price low demand of the product and vice versa so higher price will shirnk the demand of product
Ahsan Reply
a person has 60birr to buy two commodities,x and y the price of x is four birr unit the price of y is two birr unit his utility functio given by u=xy+2x determine the budget equation
Mohammed Reply
What are the various reasons for the Federal Reserve to increase the fed rates?
AMEEN Reply
What is unemployment
Mijash Reply
Unemployment is a term used to describe people who do not hold a paying job
JASON
what are the causes of unemployment
evans
unemployment refer to the situation in which people searching job but they have no. it also refers in which marginal productivity in zero.
Ramu
Causes of unemployment are: 1: Over Population 2: Break down of the family system 3: Rural/Urban Migration
Umar
unemployment simply means, in the situation where by people are looking for a job and their could achieve it.
Faruk
suppose you're the economist of ethiopia; when the country is face high rate of inflation what you recommend as one economist?
Roba Reply
if consumer spend all their incomes on consumption what does it mean?
Roba
if the government spends more of its revenue on development infrastructure from the budget it have and lower tax collection the budget deficit will run why?
Roba
because tax is less than revenue
Bhat
what is demand
Sunday Reply
Demand is the quantity of goods and services that consumers are willing and able to purchase at various prices over a given period of time
adu
the total value of goods and services produced by a coutry in it's own territorial area( mainly in a year) is called GDP
fareeha Reply
GDP- the total value of goods produced and services provided in a country during one year.
fareeha
What is the formula for propensity to save
Zubair
there is no formula for propensity to save but it has a two types one is average propensity to save and marginal propensity to save where Apc is equal to saving divide by income and mpc is equal to change in saving due change in income
Bhat
yes ooo
Sunday
yes
Ahmed
okay
kawu
what is time in economics?
Sunday
what is gross domestic product
Moonga Reply
what is macroeconomics
Dickison Reply
what is macroeconomics
Majid Reply
what is macroeconomic analysis
Deogratius Reply
Macroeconomics is a branch of the economics that studies how the aggregate economy behaves. In macroeconomics, a variety of economy-wide phenomena is thoroughly examined such as inflation, price levels, rate of growth, national income, gross domestic product (GDP) and changes in unemployment Read m
wasay
Macroeconomics is a branch of the economics that studies how the aggregate economy behaves. In macroeconomics, a variety of economy-wide phenomena is thoroughly examined such as inflation, price levels, rate of growth, national income, gross domestic product (GDP) and changes in unemployment
wasay
what is wage in economics?
Sunday
what is economic
Wajeed Reply
Economics is the social science that studies the production, distribution, and consumption of goods and services. Economics focuses on the behaviour and interactions of economic agents and how economies work. 
ninad
Economics is the brench of science that deals with the study of human behavior as it related to end or scare means which have alternative used.
Jimmy
Economics is a science that studies human behavior as a relationship between ends and scarce means which have alternative uses
Don
what is inflation
Junaid Reply
Inflation is simply a situation in an economy where there is a persistent rise or increase in the prices of goods and services in a particular year(say current year)
JERRY
It can still be defined as a situation in an economy where there's a persistent fall in the value of money
JERRY
it is the persistent rise in the general price of goods and services in an economy leading to the fall in the values of money
Muafue
It could mean the central bank has a deficit in reserve unable to cope with low export and exit of foreign investments.
Wong
inflation is the general increase in a commodity with in a country.
Jimmy
Mr Fallah please take the definition again that one is not clear
Muafue
the persistence in general price of commodities
ezechy
The persistence rise in the general price level
Muafue
The persistence rise in general price of commodities
Delhill
what is willingness
Bilal Reply
Is a person Able,Capable and Anxious to something
Muafue
Is when a person is able,capable and Anxious to do something
Muafue
thanks sir g.
Bilal
u are welcome
Muafue
where you from
Bilal
Cameroon
Muafue
And you
Muafue
Pakistan
Bilal
How far are you in Education
Muafue
who about my question What is MPC
sabawoon
is marginal propensity to consume
Muafue
a little more
sabawoon
sorry muafue sir you are little bit wrong about willingness *willingness reffers how much wants . it could be wants for payment or wants for something to do.
Masadaq
MPC reffers *How much want to consume*.
Masadaq
MPC is Marginal Propensity to Consume. MPC is proportion of additional spent on consumption.
Bon
MPC is Marginal Propensity to Consume. MPC is the proportion of additional income spent on consumption.
Bon
What is difference between GNP and GDP?
Zahid
GNP is gross national product. In calculating GNP we include net national income from abroad while GDP is gross domestic product and in calculating it we use on expenditure, income and output from within the country. My name is JERRY NGONDA from Cameron
JERRY
GNP.the total value of good $service currently produce w a given period of time by domestic owner GNP=NFI+GDP:GDP is a market value of final good $service currently produce in a given period of time w in a country boundery or territors.its take produce currently $etc
tade
yes.no suggestions
tade
good Tade Feyera
Masadaq
Tade Feyera can you send me your whatsap contact number.
Masadaq
when spending by the federal government exceeds net taxes?
stefany Reply
explain the difference between macroeconomics and microeconomics
Rahmo
Macroeconomics is the study of economics at the aggregate level while Micro is at the individual level.
Umar
Both indifference curve and isoquant do not intersect TRUE OR FALSE and justify your statement
John
what is long run and short run period
Kennedy

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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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