Lecture 4 Flashcards
What is the ‘General’ Fundamental Theorem of Finance
If there exists an equilibrium, then we have no abritrage which would mean that there exist strictly positive risk neutral probabilities & martingale pricing
What is the setting of an Arrow-Debrau Model
The Arrow-Debrau model has two time period and S different states of the world, representing the different ways in which exogenous uncertainty might be resolved between period 0 and 1 The key idea is that of a contingent commodity: a commodity whose delivery is conditional on the realized state of the world
What does an Arrow Debreu Model suggests (outcome)
The Arrow–Debreu model suggests that under certain economic assumptions (convex preferences and perfect competition) there must be a set of prices p and allocations such that aggregate supplies will equal aggregate demands for every commodity in the economy.
What three assumptions have to be satisfied for an Arrow Debreu Equilibrium
Budget Constraint Consumers choose their optimal consumption bundle Markets clear
When is trade happening in the AD model
In the Arrow-Debreu model of general equilibrium, all commodities are traded at once, no matter when they are consumed, or under what state of nature Retrading at t=1 is not necessary for the Arrow-Debreu equilibrium Even if spot markets for all the L commodities were operating at t=1 and in each state, trade in these markets would not occur
What is an asset market model
In an asset markets model consumers face a multiplicity of budget constraints, at different times and under different states of nature In asset markets equilibrium retrading at t=1 is important and agents have to correctly anticipate today the price that will prevail tomorrow-Rational Expectations
Assuming there are L goods and S states at time period 1. How many markets are there for the AD model and for the Asset market model
For the Asset Market: L*(S+1) For the AD : 2*L + S
What is Walras Law
There exists a price vector for which the excess demand is equal to zero
What is a Financial Equilibrium
It is therefore a solution to the specified problem wherein every agent i maximizes his utility subject to his budget constraints , and the goods and security markets clear. Under very general conditions, an FE exists. We should interpret observed prices as equilibrium prices.
What is the no arbitrage property and what is the intuition
No arbitrage property: If utilities are strictly increasing then in a financial equilibrium there is no arbitrage Intuition: With strictly increasing utility function the budget constraints are binding. If there was an arbitrage opportunity an agent could increase his utility without affecting his budget constraints in a negative way (remember the definition of arbitrage). Thus the budget constraints would not be binding anymore which is a contradiction. The price will adjust until equilibrium is reached
How do we price redundant securities in a financial equilibrium
They will be never traded in a FE and they will be priced via the arbitrage condition
How does pareto efficiency have anything to do with marginal rates of substitution
Sufficient condition of Pareto Optimality: The marginal rates of substitution (MRS) across states of the world are equal for all agents
Which 4 properties do Financial Equilibria have
- No arbitrage property: If utilities are strictly increasing then in a financial equilibrium there is no arbitratge 2. Redundant Securities: Redundant securities will never be traded in a Financial Equilibrium 3. When markets are complete, FE is Pareto Optimal 4. When markets are incomplete, FE is constrained Pareto Optimal (for one good, i.e. L=1)
What are the fundamentals of the lucas model
A representative agent GE model with one commodity Objective: derive the equilibrium prices of these J assets at every point in time Agent’s decision problem: How much holding to sell and how much to keep and collect the payoffs (dividends) in the following period
How much trade is going on in the Lucas Model
A representative agent will not find a counterparty to trade with since everyone demands or supplies the same –> No trade The representative agent consumes his endowment today and the dividends from the assets in the future