1. Lectures in Microeconomics-Charles W. Upton More on The Edgeworth Box

2. More on the Edgeworth Box Marginal Rates of Substitution Harry Sally Apples Bananas When they are on the contract curve, MRS S AB = MRS H AB

3. More on the Edgeworth Box Marginal Rates of Substitution Harry Sally Apples Bananas When they are on the contract curve, MRS S AB = MRS H AB If not, trading is possible. Suppose MRS S AB = 4 MRS H AB = 3 Then trade

4. More on the Edgeworth Box Two Qualifications Consumer Sovereignty

5. More on the Edgeworth Box Two Qualifications Consumer Sovereignty –Are we comfortable with welfare checks being spend on drugs and alcohol? –Do we think children know what is best for them?

6. More on the Edgeworth Box Two Qualifications Consumer Sovereignty Do we have anything to say about the right point on the contract curve?

7. More on the Edgeworth Box The Utility Possibility Frontier Sally’s Utility Harry’s Utility We construct the Utility Possibility Frontier by reading off the different levels of utility from the Contract Curve

8. More on the Edgeworth Box The Utility Possibility Frontier Sally’s Utility Harry’s Utility We construct the Utility Possibility Frontier by reading off the different levels of utility from the Contract Curve Simply another way of stating the contract curve

9. More on the Edgeworth Box The Utility Possibility Frontier Sally’s Utility Harry’s Utility We construct the Utility Possibility Frontier by reading off the different levels of utility from the Contract Curve Simply another way of stating the contract curve If we had social indifference curves for the various combinations of utility, we could find the best point along the contract curve

10. More on the Edgeworth Box The Utility Possibility Frontier Sally’s Utility Harry’s Utility

11. More on the Edgeworth Box The Core and Markets The yellow area is the core.

12. More on the Edgeworth Box The Core and Markets The yellow area is the core. If only Harry and Sally are involved, they will sit down and simply haggle with each other.

13. More on the Edgeworth Box The Core Harry Sally Apples Bananas If only Harry and Sally are involved, they will sit down and simply haggle with each other.

14. More on the Edgeworth Box The Core Harry Sally Apples Bananas If only Harry and Sally are involved, they will sit down and simply haggle with each other. Suppose there are hundreds of Harry's and Sallies?

15. More on the Edgeworth Box The Core Harry Sally Apples Bananas The normal laws of supply and demand will work and will tell us exactly where we will end up

16. More on the Edgeworth Box The Core Harry Sally Apples Bananas The normal laws of supply and demand will work and will tell us exactly where we will end up Suppose that Harry and Sally start out with (a XH,b XH ) and (a XS,b XS ).

17. More on the Edgeworth Box The Core Harry Sally Apples Bananas We tell Harry that he can buy and sell apples and bananas at prices (1,p b ). The only constraint is that (a XH - a H ) + p b (b XH - b H ) = 0

18. More on the Edgeworth Box Markets (a XH - a H ) + p b (b XH - b H ) = 0 Revenue from Apples Purchases of Bananas

19. More on the Edgeworth Box The Core Harry Sally Apples Bananas Z If Harry’s budget line is the dotted line, he will want to move to Z

20. More on the Edgeworth Box Markets If Sally is told that she can buy and sell apples and bananas subject to a budget constraint (a XS - a S ) + p b (b XS - b S ) = 0 she will be willing to buy and sell.

21. More on the Edgeworth Box Markets If Sally is told that she can buy and sell apples and bananas subject to a budget constraint (a XS - a S ) + p b (b XS - b S ) = 0 she will be willing to buy and sell. However the price that persuaded Harry to move to Z, might or might not move her to Z.

22. More on the Edgeworth Box The Fundamental Theorem For any starting point there is a price p b which will lead both Harry and Sally to move to the same point on the contract curve.

23. More on the Edgeworth Box The Fundamental Theorem For any starting point there is a price p b which will lead both Harry and Sally to move to the same point on the contract curve. That is, there is a price that equates supply and demand. It puts Harry and Sally on the contract curve

24. More on the Edgeworth Box Summary Normal trading gets Pareto Optimality in distribution. MRS(Harry ) = MRS(Sally) More to Come

25. More on the Edgeworth Box End ©2006 Charles W. Upton