We study optimal investment with multiple assets in the presence of small proportional transaction costs. Rather than computing an asymptotically optimal no-trade region, we optimize over suitable trading frequencies. We derive explicit formulas for these and the associated welfare losses due to...

We consider a market consisting of one safe and one risky asset, which offer constant investment opportunities. Taking into account both proportional transaction costs and linear price impact, we derive optimal rebalancing policies for representative investors with constant relative risk...

For portfolio choice problems with proportional transaction costs, we discuss whether or not there exists a shadow price, i.e., a least favorable frictionless market extension leading to the same optimal strategy and utility. By means of an explicit counter-example, we show that shadow prices...

This discussion paper has led to a publication in the <I>Journal of Business Ethics</I>, 2013, 117(3), 601-13.<P> Halal certification of financials product may reduce transaction costs for its buyers when it provides a trusted standard for investors that seek to comply with Islamic law. However, we show...</p></i>

This discussion paper led to a publication in (W.D. Nelson (Ed.)), <I>Advances in Business and Management</I> (pp. 1-32), New York: Nova Publishers, 2011. In this era of globalization we see an increase in specialization: the production chain issplit up in more and more parts and the production of...</i>