Article ID: | iaor20041359 |
Country: | United States |
Volume: | 26 |
Issue: | 4 |
Start Page Number: | 723 |
End Page Number: | 740 |
Publication Date: | Nov 2001 |
Journal: | Mathematics of Operations Research |
Authors: | Scarsini M., Mller A. |
We consider two random vectors X and Y, such that the components of X are dominated in the convex order by the corresponding components of Y. We want to find conditions under which this implies that any positive linear combination of the components of X is dominated in the convex order by the same positive linear combination of the components of Y. This problem has a motivation in the comparison of portfolios in terms of risk. The conditions for the above dominance will concern the dependence structure of the two random vectors X and Y, namely, the two random vectors will have a common copula and will be conditionally increasing. This new concept of dependence is strictly related to the idea of conditionally increasing in sequence, but, in addition, it is invariannt under permutation. We will actually prove that, under the above conditions, X will be dominated by Y in the directionally convex order, which yields as a corollary the dominance for positive linear combinations. This result will be applied to a portfolio optimization problem.