Title
A paradox in time-consistency in the mean-variance problem?
Abstract
We establish new conditions under which a constrained (no short-selling) time-consistent equilibrium strategy, starting at a certain time, will beat the unconstrained counterpart, as measured by the magnitude of their corresponding equilibrium mean–variance value functions. We further show that the pure strategy of solely investing in a risk-free bond can sometimes simultaneously dominate both constrained and unconstrained equilibrium strategies. With numerical experiments, we also illustrate that the constrained strategy can dominate the unconstrained one for most of the commencement dates (even more than 90%) of a prescribed planning horizon. Under a precommitment approach, the value function of an investor increases with the size of the admissible sets of strategies. However, this may fail to be true under the game-theoretic paradigm, as the constraint of time-consistency itself affects the value function differently when short-selling is and is not prohibited.
Year
DOI
Venue
2019
10.1007/s00780-018-00381-0
Finance and Stochastics
Keywords
Field
DocType
Time-consistency, Mean–variance, State-dependent risk-aversion, Equilibrium strategy, Short-selling prohibition, 60J25, 91G10, 91G80, C72, C73, G11
Bond,Magnitude (mathematics),Economics,Mathematical optimization,Time horizon,Strategy,Time consistency,Bellman equation,Precommitment
Journal
Volume
Issue
ISSN
23
1
0949-2984
Citations 
PageRank 
References 
0
0.34
4
Authors
3
Name
Order
Citations
PageRank
Alain Bensoussan1367170.17
Kwok Chuen Wong200.34
Sheung Chi Phillip Yam3335.94