How should private investors diversify? : An empirical evaluation of alternative asset allocation policies to construct a "world market portfolio"

This study evaluates the out-of-sample performance of numerous asset allocation strategies from the perspective of a Euro zone investor. Besides an increased sample period from January 1973 to December 2008, our contribution to the literature is twofold. First, we compare the performance of a broad spectrum of heuristic portfolio policies with a large set of well-established model extensions of the Markowitz (1952) mean-variance framework. Second, we explicitly differentiate between two prominent ways of diversification that are usually analyzed separately: international diversification in the stock market and diversification over different asset classes. Our analysis allows us to compare and discuss different diversification strategies to construct a "world market portfolio" that is as ex-ante efficient as possible. For international equity diversification, we find that none of the Markowitz-based portfolio models is able to significantly outperform simple heuristics. Among those, the GDP weighting dominates the traditional cap-weighted approach. In the asset allocation case, Markowitz models are again not able to beat a broad spectrum of fixed-weight alternatives out-of-sample. Analyzing more than 5000 heuristics, we find that in fact almost any form of well-balanced allocation over asset classes offers similar diversification gains as even very sophisticated and recently developed portfolio optimization approaches. Based on our findings, we suggest a simple and cost-efficient allocation approach for private investors