The aim of this paper is to review some of the concepts most frequently used to measure economic diversity at regional level, in order to focus thereafter on the description of an alternative approach developed from the financial li-terature on efficient portfolio selection. Regional real resource endowment is considered as implicit investments in productive sectors, giving shape to a regional portfolio with a level of global risk defined by its variance and re-turn, characterized in terms of output, employment and other variables. The paper explores the possibilities offered by this method to analyse the trade -off between economic growth and stability, and finally offers an application to the case of the Spanish regions during the 1978-1992 period.

Keywords: region, industry mix, efficient portfolios, economic diversity.