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Table of Contents
Overview: Introduction to Economics
Below, I have given you a general overview of the field of economics. As you work through the units of your course, you will see each of these things again in more detail. Students are often intimidated by economics … You shouldn’t be! Let me offer one word of caution, however. Economic concepts build on each other and you must be careful that you understand basic concepts in order to understand advanced concepts. If you skip a concept in Unit Two, for example, you may well have trouble understanding the concepts in Unit Six. If you have trouble understanding a concept, slow down and go back over the material as many times as necessary. Take advantage of all of the resources I’ve provided. If you stick with earlier concepts until you understand them, you’ll have little trouble with later concepts.
I. The Goals of EconomicsAs a science, economics must first develop an understanding of the processes by which human desires are fulfilled. Second, economics must show how factors that affect production and consumption lead to various results. Furthermore, it must draw conclusions that will serve to guide those who conduct and, in part, control economic activity.
II. Micro and Macro Views of the EconomyWhile there are numerous specialties within the academic field, at its most basic level economics is commonly divided into two broad areas of focus: microeconomics and macroeconomics. Microeconomics is the study of smaller levels of the economy, such as how an individual firm or a small group of firms operate. Macroeconomics is the study of whole economies or large sectors of economies.
III. Basic Economic PrinciplesBasic economic principles include the law of demand, demand determinants, the law of supply, supply determinants, market equilibrium, factors of production, the firm, gross product, as well as inflation and unemployment.
movement along the demand curve = change only in price or quantity demanded movement of entire demand curve = change in one or more demand determinants (not price or quantity)
movement along the supply curve = change only in price or quantity demanded movement of entire supply curve = change in one or more supply determinants (not price or quantity)
equilibrium: price and quantity demanded = price and quantity supplied
GNP = value of all goods and services produce by all US firms no matter where located GDP = value of all goods and services produced by all firms located in the US
IV. Schools of Economic Thought
While many basic economic principles and ideas are widely accepted by economists, there have been and continue to be differing theories about some areas of economic behavior. The following is a brief overview of the three most influential theoretical perspectives.
Basic Economic Terminology
It's extremely important that you learn and understand each of these terms. That will be easier as you start to use them. As you progress through the rest of the units, make certain you come back to this list as needed and refresh your memory. If you do that, you'll soon begin to genuinely know and understand the concepts.
EconomicsThe study of how people allocate their limited resources to satisfy their unlimited wants ... ultimate purpose of economics is to understand choices.
Microeconomics vs MacroeconomicsMicroeconomics: the part of economic analysis that studies individual decision making undertaken by individuals (or households) and by firms. Macroeconomics: the part of economic analysis that studies the behavior of the economy as a whole. It deals with economy-wide phenomena such as changes in unemployment, the general price level, and national income.
Economic BehaviorRational Self-Interest: economic assumption that individuals act as if they are motivated by self-interest and respond predictably to opportunities for gain The Rationality Assumption: the assumption that individuals will not intentionally make decisions that would leave them worse off Responding to Incentives: the reward for engaging in a given activity … people react to an incentive by making a rough comparison of costs and benefits Defining Self-Interest: the pursuit of goals that make the individual feel better off … in economic analysis goals are often measured in monetary terms although the pursuit of other goals (prestige, love, power, etc) can be analyzed using this concept
Economics as a Science
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Combination |
Price per Constant-Quality Rewritable CD |
Constant-Quality Rewritable CDs per Year |
|
A |
$5 |
40 |
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B |
$4 |
20 |
|
C |
$3 |
30 |
|
D |
$2 |
40 |
|
E |
$1 |
50 |
The Individual Demand Curve: The demand curve is a graphic representation of the demand schedule. It is a negatively sloped line showing the inverse or negative relationship between the price and the quantity demanded, meaning that if one goes up the other goes down and vice versa.
A market is any arrangement in which buyers and sellers interact to determine the price and quantity of goods and services exchanged.
Market Demand is the summation of the individual demand schedules in a market.
When price changes, there is a change in the quantity demanded and so movement along the curve.
When something other than price changes, the whole curve shifts ... there is a change in demand. Changes in non-price determinants of demand can produce a shift in the demand curve, but not movement along the demand curve.
Shifts in Demand: A movement of the entire demand curve so that at each price the quantity demanded changes. A leftward shift of the demand curve means the quantity demanded at each price decreases and is called a decrease in demand, while a rightward shift of the demand curve means the quantity demanded at each price increases and is called an increase in demand.

The Other Determinants of Demand: These are non-price factors which determine how much will be bought, other things held constant. A change in any one of these factors will cause a change in demand.
Income: For a normal good, an increase in income leads to an increase in demand, while a decrease in income leads to a decrease in demand. For an inferior good, an increase in income leads to a decrease in demand, while a decrease in income leads to an increase in demand.
A normal good is any good for which there is a direct relationship between changes in income and its demand curve. If income increases, demand for normal goods increases.
An inferior good is any good for which there is an inverse relationship between changes in income and its demand curve. As buyers’ incomes increase, demand for inferior goods decreases.

Tastes and Preferences: If consumer tastes change in favor of a good, then there is an increase in demand for it. If consumer tastes move against the good, then there is a decrease in demand for it.
Prices of Related Goods (Substitutes and Complements): When two goods are related a change in the price of one of them changes the demand for the other. Substitutes are goods that can be used to satisfy a similar want. If the price of one changes, demand for the other changes in the same direction. Complements are goods that are consumed together. If the price of one changes, the demand for the other changes in the opposite direction.
Substitute goods are goods that compete with one another for consumer purchases. If a product’s price begins to increase, the demand for similar but less expensive products (substitutes) will increase.
Complementary goods are goods that are jointly consumed with another good – coffee and cream, peanut butter and jelly, printer ink and paper. As a product’s price increases, the demand for that product and for its compliments decrease.

Expectations: Expectations of future increases in the price of a good, increases in income, and reduced availability lead to an increase in demand now. Expectations of future decreases in the price of a good, decreases in income, and increased availability lead to a decrease in demand now.
Market Size (Number of Buyers): An increase in the number of buyers in the market causes an increase in demand. A decrease in the number of buyers causes a decrease in demand.
Changes in Demand vs Changes in Quantity Demanded: A change in demand refers to a shift of the entire demand curve to the right or left if there is a change in a determinant of demand other than price. A change in quantity demanded refers to a movement along a given demand curve caused by a change in price.

The Law of Supply: the relationship between price and quantity supplied at different prices in a specified time period, other things being equal. The law of supply states that the higher the price of a good, the larger the quantity sellers will make available over a specified time, other things being constant.

Supply (4:57)
The Supply Schedule: The supply schedule is a table that shows a direct relationship between price and quantity supplied at each price in a given time period.
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Combination |
Price per Constant-Quality Rewritable CD |
Quantity of Rewritable CDs Supplied (1,000 of constant-quality units per year supplied) |
|
F |
$5 |
55 |
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G |
$4 |
40 |
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H |
$3 |
35 |
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I |
$2 |
25 |
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J |
$1 |
20 |

The Individual Supply Curve: This is a graphic representation of the supply schedule that is an upward sloping line showing a direct or positive relationship between price and quantity supplied, meaning that if one goes up the other goes up and vice versa. Supply curves have a positive slope because only at a higher price will it be profitable for sellers to incur the higher opportunity cost associated with supplying a larger quantity.
Market supply is the summation of all the quantities supplied at various prices that might prevail in the market.
When price changes there is a change in the quantity supplied and so movement along the supply curve.
When something other than price changes, the whole curve shifts. There is a change in supply. Changes in non-price determinants of demand can produce only a shift of the entire supply curve, not a movement along the supply curve.
Shifts in Supply: A change in supply is a shift of the entire supply curve so that at each price the quantity supplied changes. A leftward shift of the supply curve means that the quantity supplied at each price decreases and is called a decrease in supply, while a rightward shift of the supply curve means that quantity supplied at each price increases and is called an increase in supply.
Other Determinants of Supply: These are factors other than price which determine how much will be produced and are held constant when identifying supply. A change in one of these factors will cause the supply curve to shift.
Cost of Inputs Used to Produce the Product: An increase (decrease) in the price of one or more inputs will cause a decrease (increase) in supply.
Technology and Productivity: An improvement in technology will cause an increase in supply.
Taxes and Subsidies: Increases (decreases) in indirect taxes have the same effect as raising (lowering) costs and, thus, decreases (increases) supply. A subsidy is a negative tax.
Price Expectations: An expected increase (decrease) in the relative price of a good can lead to a decrease (increase) in supply.
Number of Firms in the Industry: If the number of firms increases (decreases), supply will increase (decrease).
Changes in Supply vs Changes in Quantity Supplied: A change in quantity supplied refers to a movement along a given supply curve caused by a change in price. A change in supply refers to a shift of the entire supply curve to the right or left caused by a change in a non-price determinant of supply.

Putting Demand and Supply
Together: Understanding how demand and supply interact is essential to
understanding how prices are determined in our economy and other economies.

Demand and Supply Schedules Combined: When the supply and demand schedules are combined, an equilibrium or market-clearing price is determined. This is a price at which quantity demanded equals quantity supplied. There is neither an excess quantity supplied (surplus) nor an excess quantity demanded (shortage).
Equilibrium: Equilibrium is a stable point. When equilibrium is reached, there is no tendency for change unless supply and/or demand change. Equilibrium is a situation where quantity supplied equals quantity demanded at a particular price. Equilibrium occurs where the supply and demand curves intersect.
A change in demand or a change in supply will cause a change in market equilibrium.
Shortages: A shortage is a situation in which quantity demanded is greater than quantity supplied. At a price below the equilibrium price there is a shortage which is corrected when price increases. Quantity demanded will fall and quantity supplied will increase until equilibrium is reached.
Surpluses: A surplus is a situation in which quantity demanded is less than quantity supplied. At a price above the equilibrium price there is a surplus that is corrected when price decreases. Quantity demanded will rise and quantity supplied will fall until equilibrium is reached.
So how do we answer the three fundamental economic questions?
(1) What to produce? (2) How to produce? (3) For whom to produce?
WHAT we produce is determined by the equilibrium of the markets.
HOW we produce is determined by profit- seeking behavior and efficient resource usage.
FOR WHOM we produce is determined by those willing and able to pay the equilibrium price.
Use these two links to gain a better understanding of the concepts: Demand and Supply Curves and Shift of Demand and Supply Curves

|
Quantity Supplied (rewritable CDs per year) |
Quantity Demanded (rewritable CDs per year) |
Difference (rewritable CDs per year) |
|
10 million |
2 million |
8 million |
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8 million |
4 million |
4 million |
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6 million |
6 million |
0 million |
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4 million |
8 million |
-4 million |
|
2 million |
10 million |
-8 million |
|
Supply is constant, demand increases. The new demand curve (DEMAND 2) is located on the right hand side of the original demand curve. The new curve intersects the original supply curve at a new point. At this point, the equilibrium price (market price) and equilibrium quantity are higher. |
Demand is constant, and supply increases. The new supply curve (SUPPLY 2) is located on the right side of the original supply curve. The new curve intersects the original demand curve at a new point. At this point, the equilibrium price (market price) is lower, and the equilibrium quantity is higher. |
The increased demand curve and increased supply are drawn together. The new intersection point is located on the right hand side of the original intersection point. The new equilibrium point indicates an equilibrium quantity higher than the original equilibrium quantity. The equilibrium price is also higher. In this case, it's because demand has increased relatively more than supply. |


An economic system in which relative prices constantly change to reflect changes in demand and supply. Prices act as signals of relative scarcity to everyone in the system.
Prices are indicators of relative scarcity and ration goods to those who are willing to pay the most. Because of scarcity, it is not possible for everyone to have everything they want. There must be some method of rationing.
Rationing by a freely functioning price system is the most efficient because all gains from mutually beneficial trade will be exhausted.
Goods can also be rationed on a “first-come, first-served” basis, by the use of political power, by physical force, by lotteries, by coupons, and by cultural, physical, and religious differences.
The rationing function of prices is often not allowed to operate when government sets price controls called price floors (minimum legal prices) and price ceilings (maximum legal prices).
If the market equilibrium cost is perceived as unfair or unjust the government can intervene in the market in a number of ways ... including banning the production and consumption of certain goods and services entirely. Government can also regulate industries such as banking that it deems too sensitive to be left alone.
A price ceiling is a legal maximum that can be charged for a good. The ceiling is shown by a horizontal line at the ceiling price, which is set below the equilibrium price. The chart shows a price ceiling of $2, at which the quantity demanded is 40 units and the quantity supplied is 20 units. The result is a shortage because the quantity demanded exceeds the quantity supplied. Rent controls are good examples of real-life price ceilings. A city might impose a ceiling of $1,000 per month on two-bedroom apartments.
Price ceilings help some groups and hurt others. For example, caps on apartment rents help tenants who pay below-market rents but hurt landlords and other prospective tenants who are shut out of the market due to the shortage. Rent-control cities are usually full of buildings that landlords abandoned because the buildings became unprofitable to operate. Because of that, the total supply of apartments is lower than it otherwise would be.
Intervention in markets should not be taken lightly because often serious by-products emerge. With apartment price ceilings,
underground markets often appear in which landlords and tenants agree to the "official" contract rate but tenants agree to make additional side payments. In addition, if landlords can't set prices, they begin to adjust the quality of their apartments, letting them fall into disrepair. Some tenants end up living in unkempt conditions and are afraid to report the landlord because they may find themselves homeless if the landlord quits renting the apartment.
A price floor is a legal minimum that can be charged for a good. The floor, as shown in the chart, is represented by a horizontal line. To be effective, the floor must be set above the equilibrium price. In the chart, the floor is set at $4. Quantity demanded is 20 units and quantity supplied is 40 units. The result of the floor is a surplus of 20 units. Common examples of price floors are found in agricultural markets such as sugar, wheat and milk. The minimum wage is also a price floor because it sets a minimum dollar amount that employers can pay employees. Therefore, there is always a "surplus" of minimum-wage workers. If employers were allowed to pay salaries at the equilibrium point, all of those surplus workers would be employed ... although all of the previous minimum-wage workers would make less.
As with price ceilings, the same tradeoff occurs between equity and efficiency with price floors. Some groups benefit while others lose. In the case of the minimum wage, those who are able to find the higher paying jobs benefit. Employers who must pay higher wages lose along with those in the labor force who cannot find jobs because wages are too high. Agricultural price floors benefit farmers at the expense of consumers. Nevertheless, society has thus far deemed the benefits received from the price floors to be worth the costs.
What happens to employment when the minimum wage is increased? New data show that minimum wage increases can lead to short-term increases in employment for some of those workers.
Quantity Restrictions: Governments can impose quantity restrictions on a market, such as a ban on ownership or trading of goods (human organs and certain psychoactive drugs). The most common quantity restrictions in international trade are import quotas. A quota is a quantity restriction that prohibits the importation of more than a specified quantity of a particular good in a one-year period. The United States has had import quotas on tobacco, sugar, and immigrant labor. The beneficiaries of quotas are importers who get the quota rights and the domestic producers of the restricted good.
We have price ceilings and price floors because of failures in the free market. A market failure is a situation in which the price system creates a problem for society or fails to achieve society’s goals. Market failure happens when competition is lacking. Two examples of market failure are income inequality and externalities.
The benefits of a price system are high levels of economic efficiency, the existence of consumer sovereignty, promotion of personal freedom, and prevention of coercion of buyers and sellers by the existence of competition. A price system can also produce market failures for which government interventions may be wanted.

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How the Price Mechanism Helps Us Make Decisions from Economics Mafia (5:35) |
The Price Mechanism in Action from Geoff Riley (22:40) |
Test Yourself: The Price System

Correcting for Externalities: An externality is a situation in which a benefit or a cost associated with an economic activity spills over to third parties, i.e., parties who are not direct participants in the market transaction. A cost is imposed on or a benefit is given to people other than the consumers and producers of a good or service (third parties).
A negative externality is one that is detrimental to third parties, such as pollution.
A positive externality is one that is beneficial to third parties, such as vaccinations or public goods.
When the supply curve fails to include negative external costs, the equilibrium price is artificially low and the equilibrium quantity is artificially high. External costs cause the market to over allocate resources, and external benefits cause the market to under allocate resources.
When externalities are present, market failure gives incorrect price and quantity signals, and resources are misallocated.

Special Taxes: Taxes on output would reduce output, but would not provide an incentive to reduce pollution per unit of output. Taxes on the amount of pollutants emitted would provide an incentive to reduce pollution per unit of output.
Regulation: The government could specify a maximum allowable rate of pollution.
Government Financing and Production: When positive externalities are large (e.g. public goods), government may finance and produce the good or service.
Subsidies: A subsidy is a negative tax: a payment to the consumer or producer of a good or service for consuming or producing that good or service
Regulation: Government can require that certain actions be undertaken, e.g. inoculations of school children.
Providing a Legal System: All relationships among consumers and businesses are governed by legal rules. Much of the legal system is involved with defining and protecting property rights.
Promoting Competition:
Promoting competition is a way of increasing the efficiency of the economy. Antitrust
legislation is used to reduce the power of monopolies and to discourage certain
activities that restrain trade.
Providing Public Goods: Public goods are goods to which the principle of rival consumption does not apply (rival vs non-rival) and are jointly consumed by many individuals simultaneously (excludable vs non-excludable). This is in contrast to private goods that can be consumed by only one person at a time.
A public good is a good that, once produced, has two properties: (1) users collectively consume benefits and (2) no one can be excluded. National defense, public education and roads are examples of public goods.
If public goods are available only in the marketplace, people wait for someone else to pay. The result is an underproduction or zero production of public goods.
Characteristics
of Public Goods
Public goods can be used by more and more people at no additional cost and without depriving others of any services of the goods.
It is difficult to design a collection system for a public good on the basis of how much individuals use it.
Free Riders
The free rider problem is a situation associated with public goods when individuals presume others will pay for public goods, so they can escape paying for their portion without causing a reduction in production.
Merit and Demerit Goods: The government defines certain goods and services as desirable or undesirable. A merit good is a good that has been deemed socially desirable by the political process, and will be provided by government or subsidized. A demerit good is a good that has been deemed socially undesirable by the political process. It will be prohibited, taxed, or regulated to reduce consumption.
Income Redistribution:
Government explicitly redistributes income by progressive taxation and by transfer
payments and transfers in kind. Transfer payments are money payments made to individuals
for which no services or goods are concurrently rendered. Transfers in kind are
payments in the form of goods and services for which no goods or services are concurrently
rendered.
The Role of Government in the Economy
Positive and Negative Externalities
Inequality.org works on exposing the wealth gap.
Longer Commutes, Shorter Lives: The Costs of Not Investing in America
Ensuring Economy-wide Stability: The federal government is charged under the Employment Act of 1946 with stabilizing the economy at high levels of employment.
Fiscal Policy
Fiscal policy is a broad term used to refer to the tax and spending policies of the federal government. For example, when demand is low in the economy, the government can step in and increase its spending to stimulate demand. Or it can lower taxes to increase disposable income for people as well as corporations. Fiscal policy decisions are determined by Congress and the Executive branch.
Monetary Policy
Monetary policy is a term used to refer to the actions of central banks to achieve macroeconomic policy objectives such as price stability, full employment and stable economic growth. In the US, Congress established maximum employment and price stability as the macroeconomic objectives for the Federal Reserve. They are sometimes referred to as the Federal Reserve's dual mandate. Apart from these overarching objectives, Congress determined that operational conduct of monetary policy should be free from political influence. As a result, the Federal Reserve is an independent agency of the federal government.
The Business Cycle
The business cycle is comprised of four phases of economic growth and decline. It's sometimes called the boom and bust cycle. The goal of economic policy is to keep the economy growing at a healthy rate -- fast enough to create jobs for everyone who wants one, but slow enough to avoid inflation. The business cycle is caused by the forces of supply and demand, the availability of capital and expectations about the future.
There are four phases that describe the business cycle. At any point in time the economy is in one of these stages:
Contraction: The economy starts slowing down. It's usually accompanied by a bear market. GDP growth rates usually slow to the 1%-2% level before actually turning negative. A contraction is usually triggered by an event, such as a rapid increase in interest rates, a financial crisis or runaway inflation. Fear and panic replace confidence. Investors sell stocks, and buy bonds, gold and the US dollar. Consumers lose their jobs, sell their homes and stop buying anything but necessities. Businesses lay off workers and hoard cash. At this point, a stock market correction may indicate that assets are overvalued. The Fed can switch to expansionary monetary policy if economic growth slows or even turns negative. That means it will lower interest rates and buy Treasuries in open market operations. This is when expansionary fiscal policy is desperately needed. That means cutting taxes and increasing spending to create jobs, demand and confidence.
Trough: The economy hits bottom, usually in a recession. GDP growth may still be negative, but it's not as bad. It's clear that the economy has turned a corner. Confidence must be restored before the economy can enter a new expansion phase. That often requires intervention with monetary or fiscal policy. Central banks pull out all the tools to jump start the economy out of a trough.
Expansion: The economy starts growing again. It's usually signaled by a bull market. GDP growth turns positive again, and should be in the healthy 2%-3% range. If the economy is managed well, it can stay in the expansion phase for years. When consumers are confident, they buy because they know there will be future income from better jobs, higher home values and increasing stock prices. As demand increases, businesses hire new workers, which increases income, further stimulating more demand. Too much capital will turn a healthy expansion into a peak. That's because there's too much money chasing too few goods. This causes inflation. Central banks try to keep the core inflation rate at around 2% to create a healthy expectation of inflation. In the United States, that means the Federal Reserve will keep the Fed funds rate right around 2%. If economic growth remains at the healthy 2-3% growth rate, the Fed won't make any changes.
Peak: The economy is overheated, and is in a state of "irrational exuberance." This is when inflation may hit. The economy's expansion slows. It's usually the last healthy growth quarter before contraction starts. You usually don't know you are in a peak until it is too late. However, if the GDP growth rate is 4% or higher for two or more quarters in a row, the peak is not far off. If demand outstrips supply, then the economy can overheat. In addition, investors and businesses compete to outperform the market, taking on more risk to gain some extra return. You can usually recognize a peak by two things: First, the media says that the expansion will never end. Second, it seems everyone and his brother is making tons of money from whatever the asset bubble is. Central banks use contractionary monetary policy during an expansion to avoid the irrational exuberance of a peak. That means they raise interest rates. If needed, they will sell Treasuries and other assets during open market operations.
The National Bureau of Economic Research (NBER) analyzes economic indicators to determine the phases of the business cycle. The Business Cycle Dating Committee uses quarterly GDP growth rates as the primary indicator of economic activity. The Bureau also uses monthly figures, such as employment, real personal income, industrial production and retail sales. For this reason, the NBER has the final say on economic expansions and contractions, or business cycles.
Comparing the Broad Social Goals of Command and Market Economies (PDF)
Fiscal Policy Vocabulary (PDF)
Ben Casselman of the NYT wrote a good explainer of recession definitions.
Check out the St. Louis Fed's presentation The Financial Crisis: What Happened?. The original video is no longer available but you can view the power point presentation.
A stock market slump doesn't have to mean a recession is near.
It's not just vibes. Americans' perception of the economy has completely changed. Americans' perception of the economy has completely changed. The Covid pandemic upended the factors that used to predict consumer sentiment. Before the pandemic, important variables seemed to be vehicle sales, gas prices, median household income, the federal funds effective rate, personal savings and household expenditures (excluding food and energy). Some of these indicators saw dramatic changes after the pandemic, likely contributing to the disconnect between later positive economic news and Americans' continued economic pessimism. But looking at the same data from 2021 to 2024, researchers found that not a single variable showed up as a statistically significant predictor of consumer sentiment. That suggests there's something much more complicated going on behind the scenes. There’s a notable shift from the pre-pandemic times, when we had a relatively clear sense of which variables were related to consumers' feelings and in what kinds of ways.
What Washing Machines Can Tell Us about America’s Economic Future
What Is a Stock Market Correction?
Test Yourself: Government Functions in the Economy

One of the main basic economic models is the circular-flow model, which describes the flow of money and products throughout the economy in a very simplified way. The model represents all of the actors in an economy as either households or firms (companies), and it divides markets into two categories:
o markets for goods and services (product markets)
o markets for factors of production (factor markets)
(Remember, a market is just a place where buyers and sellers come together to generate economic activity.)
The concept of a circular flow of income involves two principles; (1) in every economic exchange, the seller receives exactly the same amount that the buyer spends and (2) goods and services flow in one direction and money payments flow in the other. (Note that money, by definition, flows from buyer to seller in all markets.)
Profits are a part of costs because entrepreneurs must be rewarded for providing their services, or they will not provide them.
Total income is the total of all individuals’ income and is also defined as the annual cost of producing the entire output of final goods and services. Total output is the value of all of the final goods and services produced in the economy during the year.
Product Markets: Households are the buyers and businesses are the sellers of consumer goods. Households buy finished products from firms that are looking to sell what they make. In this transaction, money flows from households to firms. Finished products flow from firms to households in product markets.
Factor Markets: Households are the sellers; they sell resources such as labor, land, capital and entrepreneurial ability. If markets for goods and services were the only markets available, firms would eventually have all of the money in an economy, households would have all of the finished products, and economic activity would stop. Luckily, product markets don’t tell the whole story, and factor markets serve to complete the circular flow of money and resources.
The term factors of production refers to anything that is used by a firm in order to make a final product.
Some examples of factors of production are labor (the work done by people), capital (the machines used to makes products), land and so on. Labor markets are the most commonly discussed form of a factor market, but it’s important to remember that factors of production can take many forms.
In factor markets, households and firms play different roles than they do in product markets. When households provide labor to firms, they can be thought of as the sellers of their time or work product. (Technically, employees can more accurately be thought of as being rented rather than being sold, but this is usually an unnecessary distinction.) Firms provide money to households as compensation for the use of factors of production. Therefore, the functions of households and firms are reversed in factor markets as compared to in product markets.
Total income is income earned by households in payment for the production of these goods and services. The value of total output is identical to total income, since spending by one group is income to another.
When factor markets are put together with product markets, a closed loop for the flow of money is formed. As a result, continued economic activity is sustainable in the long run, since neither firms nor households are going to end up with all of the money. (It’s also worth noting that firms are owned by people, and people are parts of households, so the two entities are not quite as distinct as the model implies.) Firms use factors of production to create finished products and households consume finished products in order to maintain their ability to provide factors of production.

The basic circular flow of income, or two-sector circular flow of income model, consists of six assumptions:
The economy consists of two sectors: households and firms.
Households spend all of their income (Y) on goods and services or consumption (C). There is no saving (S).
All output (O) produced by firms is purchased by households through their expenditure (E).
There is no financial sector.
There is no government sector.
There is no foreign sector
This model is simplified in a number of ways, most notably in that it represents a pure capitalistic economy with no role for government. One could, however, extend this model to incorporate government intervention by inserting government between the households, firms, and markets. (See model below.)
It’s interesting to note that there are four places where government could be inserted into the model, and each point of intervention is realistic for some markets and not for others. (For example, an income tax could be represented by a government entity being inserted between households and factor markets, and a tax on a producer could be represented by inserting government between firms and goods and services markets.)
In the five-sector model the economy is divided into five sectors:
Household sector
Firms or Producing sector
Financial sector: banks and non-bank intermediaries who engage in the borrowing (savings from households) and lending of money
Government sector: consists of the economic activities of local, state and federal governments.
International sector: transforms the model from a closed economy to an open economy.
The five sector model of the circular flow of income is a more realistic representation of the economy. Unlike the two sector model where there are six assumptions the five sector circular flow relaxes all six assumptions. Since the first assumption is relaxed there are three more sectors introduced.
In general, the circular-flow model is useful because it informs the creation of the supply and demand model. When discussing the supply and demand for a good or service, it is appropriate for households to be on the demand side and firms to be on the supply side, but the opposite is true when modeling the supply and demand for labor or another factor of production.

One common question regarding this model is what it means for households to provide capital and other non-labor factors of production to firms. In this case, it’s important to remember that capital refers not only to physical machinery but also to the funds (sometimes called financial capital) that are used to buy the machinery used in production. These funds flow from households to firms every time people invest in companies via stocks, bonds or other forms of investment.
Households then get a return on their financial capital in the form of stock dividends, bond payments and the like, just as households get a return on their labor in the form of wages.
Leakages and injections
In the five sector model there are leakages and injections.
o Leakage means withdrawal from the flow. When households and firms save part of their incomes it constitutes leakage. Leakages may be in form of savings, tax payments or imports. Leakages reduce the flow of income.
o Injection means introduction of income into the flow. When households and firms borrow savings, that constitutes injections. Injections increase the flow of income. Injections can take the forms of (a) investment, (b) government spending or (c) exports. So long as leakages are equal to injections the circular flow continues indefinitely. Financial institutions or the capital market play the role of intermediaries.
Leakages and injections can occur in the financial sector, government sector and international sector:
1. In the financial sector
In terms of leakages in the circular flow, financial institutions provide the option for households to save their money. This is a leakage because the saved money cannot be spent in the economy and thus is an idle asset so that not all output will be purchased. In terms of injections, the financial sector provides investment (I) in the business/firms sector.
2. In the government sector
The leakages in the government sector occur with the collection of revenue through Taxes (T) provided by households and firms to the government. Taxes are a leakage because it reduces current income thus reducing expenditures on current goods and services. Injection provided by the government sector occur via government spending (G) that provides collective services and welfare payments to the community.
3. In the international sector
The main leakage from the international sector occurs because of imports (M), which represent spending outside the country by residents. The main injection provided by this sector is the exports of goods and services. Those exports generate income coming into the country for domestic exporters
from overseas buyers.
Summary of leakages and injections
LEAKAGES
INJECTIONS
Saving (S)
Investment (I)
Taxes (T)
Government Spending (G)
Imports (M)
Exports (X)
Test Yourself: The Circular Flow

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