Abstract/Summary

A multicurrency numéraire is a weighted basket of currencies, where the weights sum to zero and all weights are positive. A stable aggregate currency is an optimal multicurrency numéraire, which is estimated using a minimum-variance portfolio optimisation. The variables of the portfolio optimisation are invariant currency indexes, which are multilateral exchange rates and are priced in terms of an equally-weighted basket of the currencies. This paper shows that there are some fundamental issues with the concept of a stable aggregate currency. Once these issues have been resolved, it is shown that the portfolio optimisation problem is infeasible.