1. Economic Models: Tradeoffs and Trade Chapter 2
Slides created by Dr. Amy Scott
©2010  Worth Publishers 1

2. TUNNEL VISION
A miniature airplane sitting motionless in a wind tunnel isn’t the same thing as an actual aircraft in flight.
But it is a very useful model of a flying plane.
Economic theory consists mainly of a collection of models.
In this chapter, we will look at two economic models that illustrate why such models are so useful. 2

3. Chapter Objectives Why models in economics?
Three simple but important models:
Production possibility frontier
Comparative advantage
Circular-flow diagram
Positive economics and normative economics.
When economists agree and why they sometimes disagree.

4. Models in Economics
A model is a simplified representation of a real situation - used to better understand real-life situations.
Models play a crucial role in economics
Used to study a real but simplified economy
Ex.: Cigarettes as currency in World War II prison camps
Used to simulate an economy on a computer
Ex.: Use Tax models to study impact of proposed study
The “other things equal” (ceteris paribus) assumption means that all other relevant factors remain unchanged.

5. Models for Money
An economic model can be worth quite a bit of money. Global Insight, the world’s biggest consulting firm, uses economic models to predict future trends and give advice to firms and governments.
A particularly lucrative branch is finance theory which calculates what assets, such as shares in a company, are worth.
The most famous business application of finance theory was Long Term Capital Management, a fund that used sophisticated models to invest money for its wealthy clients.
The fund did well for a while, then it collapsed. People feared companies would be brought down with it but the government organized a rescue operation. A similar situation almost happened in the fall of 2008.

6. Three Models The Production Possibility Frontier
Illustrates trade-offs facing an economy that produces only two goods.
It shows the maximum quantity of one good that can be produced for any given production of the other.
The PPF improves our understanding of trade-offs by considering a simplified economy
that produces only two goods
by showing this trade-off graphically.
if a castaway devotes resources to catching fish, he cannot use those same resources to gather coconuts.
What to do?
Even a castaway faces trade-offs.

7. Opportunity Cost and Slope of PPF
If the tradeoff remains constant along the PPF then we say they face a Constant Opportunity Cost and the PPF has a linear slope.
If the tradeoff increases along the PPF than we say they face an Increasing Opportunity Cost and the PPF has a nonlinear slope.

8. The Production Possibility Frontier with Constant Opportunity Cost
Quantity of coconuts 30 D
Feasible and
efficient
in production
Not feasible A 15
Figure Caption:
Figure The Production Possibility Frontier
The production possibility frontier illustrates the trade-offs facing an economy that produces two goods. It shows the maximum quantity of one good that can be produced given the quantity of the other good produced. Here, the maximum quantity of coconuts that Tom can gather depends on the quantity of fish he catches, and vice versa. His feasible production is shown by the area inside or on the curve. Production at point C is feasible but not efficient. Points A and B are feasible and efficient in production, but point D is not feasible.
Feasible but
not efficient B 9 C
Production possibility frontier
PPF 20 28 40
Quantity of fish

9. PPF with Increasing Opportunity Cost
Producing the first
20 fish . . .
…requires giving up
5 coconuts
Quantity of coconuts 35 30
But producing
20 more fish . . . A 25 20
…requires giving up
25 more coconuts… 15
Figure Caption:
Figure Increasing Opportunity Cost
The bowed-out shape of the production possibility frontier reflects increasing opportunity cost. In this example, to produce the first 20 fish, Tom must give up 5 coconuts. But to produce an additional 20 fish, he must give up 25 more coconuts. 10 5
PPF 10 20 30 40 50
Quantity of fish

10. Economic Growth
Economic Growth is the growing ability of the economy to produce goods and services
Economic Growth can come from two sources:
Increase in Factors of Production – resources used to produce goods and services (Land, Labor and Capital)
Technological Improvement – improvement in the technical means of producing goods and services

11. Economic Growth
Economic growth results in an outward shift of the PPF because production possibilities are expanded.
Quantity of coconuts 35 E
The economy can now produce more of everything. 30 A 25 20
Production is initially at point A (20 fish and 25 coconuts),  it can move to point E (25 fish and 30 coconuts). 15
Figure Economic Growth
Economic growth results in an outward shift of the production possibility frontier because production possibilities are expanded. The economy can now produce more of everything. For example, if production is initially at point A (20 fish and 25 coconuts), it could move to point E (25 fish and 30 coconuts). 10 5
Original
New
PPF
PPF 10 20 25 30 40 50
Quantity of fish

12. Production Possibilities for Two Castaways
Quantity of coconuts
(a) Tom’s Production Possibilities 30
Tom’s consumption
without trade
Figure Caption:
Figure Production Possibilities for Two Castaways
Here, each of the two castaways has a constant opportunity cost of fish and a straight-line production possibility frontier. In Tom’s case, each fish always has an opportunity cost of 3⁄4 of a coconut. 9
Tom’s
PPF 28 40
Quantity of fish

13. Production Possibilities for Two Castaways
Quantity of coconuts
(a) Hank’s Production Possibilities 20
Hank’s consumption
without trade
Figure Caption:
Figure Production Possibilities for Two Castaways
Here, each of the two castaways has a constant opportunity cost of fish and a straight-line production possibility frontier. In Hank’s case, each fish always has an opportunity cost of 2 coconuts. 8
Hank’s
PPF 6 10
Quantity of fish

14. Tom and Hank’s Opportunity Costs
Tom’s Opportunity Cost
Hank’s Opportunity Cost
One fish
3/4 coconut
2 coconuts
One coconut
4/3 fish
1/2 fish
To catch another Fish, Tom must give up ¾ of a coconut.
To catch another Fish, Hank must give up 2 coconuts.
Tom gives up less for another fish (has a lower opportunity cost) so Tom will fish.
By necessity, Hank will gather coconuts – but also because to gather another coconut, Tom must give up 4/3 of a Fish while Hank only has to give up ½ of a Fish. Hank gives up less (has a lower opportunity cost) so Hank will gather coconunts

15. Specialize and Trade
Both castaways are better off when they each specialize in what they are good at and trade.
It’s a good idea for Tom to catch the fish for both of them, because his opportunity cost of a fish in terms of coconuts not gathered is only 3/4 of a coconut, versus 2 coconuts for Hank.
Correspondingly, it’s a good idea for Hank to gather coconuts for the both of them. His opportunity costs is less, only 1/2 of a fish to 4/3 fish for Tom.

16. Comparative Advantage and Gains from Trade
(a) Tom’s Production and Consumption
(b) Hank’s Production and Consumption
Quantity of coconuts
Quantity of coconuts 30
Tom’s consumption without trade
Hank’s production with trade
Tom’s consumption with trade 20
Hank’s consumption with trade
Tom’s production with trade 10
Figure Caption:
Figure 2-5: Comparative Advantage and Gains from Trade By specializing and trading, the two castaways can produce
By specializing and trading, the two castaways can produce and consume more of both goods. Tom specializes in catching fish, his comparative advantage, and Hank— who has an absolute disadvantage in both goods but a comparative advantage in coconuts—specializes in gathering coconuts. The result is that each castaway can consume more of both goods than either could without trade. 10
Hank’s consumption without trade 9 8 T o m 's
Hank's
PPF
PPF 28 30 40 6 10
Quantity of fish
Quantity of fish

17. How the Castaways Gain from Trade
Both Tom and Hank experience gains from trade:
Tom’s consumption of fish increases by two, and his consumption of coconuts increases by one.
Hank’s consumption of fish increases by four, and his consumption of coconuts increases by two.

18. Comparative vs. Absolute Advantage
An individual has a comparative advantage in producing a good or service if the opportunity cost of producing the good is lower for that individual than for other people.
An individual has an absolute advantage in an activity if he or she can do it better than other people.
Having an absolute advantage is not the same thing as having a comparative advantage. You can have an absolute advantage in both goods and still benefit from trade.

19. Tom vs. Hank – Absolute vs. Comparative
Tom has an absolute advantage in both activities: he can produce more output with a given amount of input (in this case, his time) than Hank.
But Tom can indeed benefit from a deal with Hank because comparative, not absolute, advantage is the basis for mutual gain.
So Hank, despite his absolute disadvantage, even in coconuts, has a comparative advantage in coconut gathering.
Meanwhile Tom, who can use his time better by catching fish, has a comparative disadvantage in coconut-gathering.

20. Comparative Advantage and International Trade
(a) The U.S. Production Possibilities Frontier
(b) Canadian Production Possibilities Frontier
Quantity of aircraft
Quantity of aircraft
3,000
Canadian production with trade
U.S. consumption without trade
Canadian consumption without trade
U.S. consumption with trade
2,000
1,500
1,500
U.S. production with trade
Canadian consumption with trade
1,000
Figure Caption:
Figure 2.6: Comparative Advantage and International Trade
In this hypothetical example, Canada and the United States produce only two goods: pork and aircraft. Aircraft are measured on the vertical axis and pork on the horizontal axis. Panel (a) shows the U.S. production possibility frontier. It is relatively flat, implying that the United States has a comparative advantage in pork production. Panel (b) shows the Canadian production possibility frontier. It is relatively steep, implying that Canada has a comparative advantage in aircraft production. Just like two individuals, both countries gain from specialization and trade. U
.S.
Canadian
PPF
PPF 1 2 3
0.5 1
1.5
Quantity of pork (millions of tons)
Quantity of pork (millions of tons)

21. Comparative Advantage and International Trade
Just like the example of Tom and Hank, the U.S. and Canada can both achieve mutual gains from trade.
If the U.S. concentrates on producing pork and ships some of its output to Canada, while Canada concentrates on aircraft and ships some of its output to the U.S., both countries can consume more than if they insisted on being self-sufficient.

22. PITFALLS Misunderstanding Comparative Advantage
A common mistake is to confuse comparative advantage with absolute advantage.
Ex.: U.S. vs. Japan in 1980s:
Commentators: “U.S. might soon have no comparative advantage in anything”
Wrong! They meant “absolute advantage”

23. Pajama Republics
Poor countries tend to have low productivity in clothing manufacturing but even lower productivity in other industries.
Comparing per capita income with the share of the clothing industry in manufacturing employment shows a strong effect.

24. Transactions: The Circular-Flow Diagram
Trade takes the form of barter when people directly exchange goods or services they have for goods or services they want.
The circular-flow diagram is a model that represents the transactions in an economy by flows around a circle.
Households buy goods and services from firms
Firms buy factors of production from households
Inner Flow = goods and services
Outer Flow = money

25. The Circular-Flow Diagram
Money
Households
Money
Goods
Factors
and
services
Markets for goods and services
Factor Markets
Figure Caption:
Figure 2.7: The Circular-Flow Diagram
This diagram represents the flows of money and goods and services in the economy. In the markets for goods and services, households purchase goods and services from firms, generating a flow of money to the firms and a flow of goods and services to the households. The money flows back to households as firms purchase factors of production from the households in factor markets.
Goods
and
Factors
services
Firms
Money
Money

26. Circular-Flow of Economic Activities
A household is a person or a group of people that share their income.
A firm is an organization that produces goods and services for sale.
The markets for goods and services is where firms sell goods and services that they produce to households.
The factor markets are where firms buy the resources they need to produce—factors of production.

27. Circular-Flow of Economic Activities
Ultimately, factor markets determine the economy’s income distribution: how total income is divided among the owners of the various factors of production.

28. Rich Nation, Poor Nation
Look at the labels inside your clothing.
Most clothing is manufactured outside of the United States.
These countries are typically much poorer than the United States usually because they are less productive-they cannot produce as much from a given quantity of resources as comparable firms in the United States.
This is ‘comparative advantage’ – they can make clothing at a lower opportunity cost than the US – while the US can make other goods at a lower opportunity cost.

29. True or False? An increase in the amount of resources available to Tom for use in producing coconuts and fish does not change his production possibility frontier.
True
False

30. True or False? A technological change that allows Tom to catch more fish for any amount of coconuts gathered results in a change in his production possibility frontier.
True
False

31. True or False? The production possibility frontier is useful because it illustrates how much of one good an economy must give up to get more of another good regardless of whether resources are being used efficiently.
True
False

32. In Italy, an automobile can be produced by 8 workers in one day and a washing machine by 3 workers in one day. In the United States, an automobile can be produced by 6 workers in one day, and a washing machine by 2 workers in one day.
Which country has an absolute advantage in the production of automobiles?
Italy
United States
Which country has an absolute advantage in the production of washing machines?
Italy
United States

33. In Italy, an automobile can be produced by 8 workers in one day and a washing machine by 3 workers in one day. In the United States, an automobile can be produced by 6 workers in one day, and a washing machine by 2 workers in one day.
Which country has a comparative advantage in the production of washing machines?
Italy
United States
Which country has a comparative advantage in the production of automobiles?
Italy
United States

34. In Italy, an automobile can be produced by 8 workers in one day and a washing machine by 3 workers in one day. In the United States, an automobile can be produced by 6 workers in one day, and a washing machine by 2 workers in one day.
What pattern of specialization results in the greatest gains from trade between the two countries?
Italy specializes in automobiles and the U.S. specializes in washing machines.
Italy specializes in washing machines and the U.S. specializes in automobiles.

35. Use the Circular-Flow Diagram to determine if the statement is true or false: An increase in household spending leads to an increase in jobs in the economy.
True
False

36. Positive vs. Normative Economics
Positive economics is the branch of economic analysis that describes the way the economy actually works.
Statement of fact
‘what is’
Normative economics makes prescriptions about the way the economy should work.
Statement of opinion
‘what ought to be’
A forecast is a simple prediction of the future.

37. Positive vs. Normative Economics
Economists can determine correct answers for positive questions, but typically not for normative questions, which involve value judgments.
There are exceptions are when policies designed to achieve a certain prescription can be clearly ranked in terms of efficiency.
It is important to understand that economists don’t use complex models to show “how clever they are,” but rather because they are “not clever enough” to analyze the real world as it is.

38. When and Why Economists Disagree
There are two main points on which economists disagree:
Which simplifications to make in a model
Values

39. When Economists Agree
“If all the economists in the world were laid end to end, they still couldn’t reach a conclusion”
A survey by the American Economic Association published in May of 1992 in the American Economic Review reported that in fact many economists do agree.
At the top, more than 90 percent of the economists agreed that tariffs and import quotas usually reduce general economic welfare.
There is a lot of common ground but also much disagreement.

40. Economists in Government
Economists play an important role in the business world and also in government.
One of their most important functions is to make economic policy.
In the United States, a key role is played by the Council of Economic Advisors.
Economists are also active in the Bureau of Labor Statistics and the Federal Reserve as well as the World Bank and the International Monetary Fund.

41. Which of the following statements is a positive statement?
Which of the following statements is a positive statement?
Society should take measures to prevent people from engaging in dangerous personal behavior.
People who engage in dangerous personal behavior impose higher costs on society through higher medical costs.
both A and B
none of the above

42. Policy choice A and policy choice B attempt to achieve the same social goal. Policy choice A, however, results in a much less efficient use of resources than policy choice B. Therefore economists are more likely to agree on choosing policy choice B.
True
False

43. When two economists disagree on the desirability of a policy, it’s typically because one of them has made a mistake.
True
False

44. Policy makers can always use economics to figure out which goals a society should try to achieve.
True
False

45. 1 of 3
Summary
Almost all economics is based on models. An important assumption in economic models is the other things equal assumption (ceteris paribus), which allows analysis of the effect of a change in one factor by holding all other relevant factors unchanged.
One important economic model is the production possibility frontier. It illustrates: opportunity cost, efficiency, and economic growth. There are two basic sources of growth: an increase in factors of production, resources such as land, labor, capital, and human capital, inputs that are not used up in production, and improved technology.

46. 2 of 3
Summary
Another important model is comparative advantage, which explains the source of gains from trade between individuals and countries. Everyone has a comparative advantage in something. This is often confused with absolute advantage, an ability to produce a particular good or service better than anyone else.
In the simplest economies, people barter or trade goods and services for one another—rather than trade them for money, as in a modern economy. The circular-flow diagram represents transactions within the economy as flows of goods, services, and money between households and firms. These transactions occur in markets for goods and services and factor markets.

47. 3 of 3
Summary
Economists use economic models both for positive economics, which describes how the economy works, and for normative economics, which prescribes how the economy should work. Positive economics often involves making forecasts. Economists can determine correct answers for positive questions, but typically not for normative questions, which involve value judgments.
There are two main reasons economists disagree. One, they may disagree about which simplifications to make in a model. Two, economists may disagree—like everyone else—about values.

48. Coming attraction Chapter 3: Supply and Demand
The End of Chapter 2
Coming attraction Chapter 3: Supply and Demand 48