The Portfolio Selection Model developed by Markowitz in the 1950s offers a theore- cally founded approach to combining securities into a utility-optimizing investment portfolio, that is, a portfolio leading to the best possible trade-off between the expected return and investment risk. However, when applied in practice, the model often rea- es its limits as soon as certain central assumptions are not fulfilled. This holds es- cially for the assumption of perfect liquidity of all assets in the portfolio, that is, the ability of selling or buying any of these assets at any time immediately and...