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ECON 251: Financial Theory

Lecture 12 - Overlapping Generations Models of the Economy. In order for Social Security to work, people have to believe there's some possibility that the world will last forever, so that each old generation will have a young generation to support it. The overlapping generations model, invented by Allais and Samuelson but here augmented with land, represents such a situation. Financial equilibrium can again be reduced to general equilibrium. At first glance it would seem that the model requires a solution of an infinite number of supply equals demand equations, one for each time period. But by assuming stationarity, the whole analysis can be reduced to one equation. In this mathematical framework we reach an even more precise and subtle understanding of Social Security and the real rate of interest. We find that Social Security likely increases the real rate of interest. The presence of land, an infinitely lived asset that pays a perpetual dividend, forces the real rate of interest to be positive, exposing the flaw in Samuelson's contention that Social Security is a giant, yet beneficial, Ponzi scheme where each generation can win by perpetually deferring a growing cost. (from oyc.yale.edu)

Lecture 12 - Overlapping Generations Models of the Economy

Time Lecture Chapters
[00:00:00] 1. Introduction to the Overlapping Generation Model
[00:12:59] 2. Financial and General Equilibrium in Social Security
[00:26:37] 3. Present Value Analysis of Social Security
[00:59:24] 4. Real Rate of Interest and Social Security

References
Lecture 12 - Overlapping Generations Models of the Economy
Instructor: Professor John Geanakoplos. Transcript [html]. Audio [mp3]. Download Video [mov].

Go to the Course Home or watch other lectures:

Lecture 01 - Why Finance?
Lecture 02 - Utilities, Endowments, and Equilibrium
Lecture 03 - Computing Equilibrium
Lecture 04 - Efficiency, Assets, and Time
Lecture 05 - Present Value Prices and the Real Rate of Interest
Lecture 06 - Irving Fisher's Impatience Theory of Interest
Lecture 07 - Shakespeare's Merchant of Venice and Collateral, Present Value and the Vocabulary of Finance
Lecture 08 - How a Long-Lived Institution Figures an Annual Budget; Yield
Lecture 09 - Yield Curve Arbitrage
Lecture 10 - Dynamic Present Value
Lecture 11 - Social Security
Lecture 12 - Overlapping Generations Models of the Economy
Lecture 13 - Demography and Asset Pricing: Will the Stock Market Decline when the Baby Boomers Retire?
Lecture 14 - Quantifying Uncertainty and Risk
Lecture 15 - Uncertainty and the Rational Expectations Hypothesis
Lecture 16 - Backward Induction and Optimal Stopping Times
Lecture 17 - Callable Bonds and the Mortgage Prepayment Option
Lecture 18 - Modeling Mortgage Prepayments and Valuing Mortgages
Lecture 19 - History of the Mortgage Market: A Personal Narrative
Lecture 20 - Dynamic Hedging
Lecture 21 - Dynamic Hedging and Average Life
Lecture 22 - Risk Aversion and the Capital Asset Pricing Theorem
Lecture 23 - The Mutual Fund Theorem and Covariance Pricing Theorems
Lecture 24 - Risk, Return, and Social Security
Lecture 25 - The Leverage Cycle and the Subprime Mortgage Crisis
Lecture 26 - The Leverage Cycle and Crashes