SFB 303 Discussion Paper No. A - 599

 
Author: Aliprantis C. D. , D. Brown and J. Werner
 
Title: Minimum-Cost Portfolio Insurance
 
Abstract:  
Minimum-cost portfolio insurance is an investment strategy that enables an 
investor to avoid losses while still capturing  gains of a payoff of a portfolio 
at minimum cost. If derivative markets are complete, then holding a put option in 
conjunction with the reference portfolio provides minimum-cost insurance at arbitrary 
arbitrage-free security prices. We derive a characterization of incomplete derivative 
markets in which the minimum-cost portfolio insurance is independent of arbitrage-free 
security prices. 
 
Our characterization relies on the theory of lattice-subspaces. We establish that a 
necessary and sufficient condition for price-independent minimum-cost portfolio 
insurance is that the asset span is a lattice-subspace of the space of contingent claims. 
If the asset span is a lattice-subspace, then the minimum-cost portfolio insurance 
can be easily calculated as a portfolio that replicates the targeted payoff 
in a subset of states which is the same for every reference portfolio. 
 
Keywords: Portfolio insurance, derivative markets, lattice-subspace
 
JEL-Classification-Number: G11, G12
 
Creation-Date: July 1999
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