International Portfolio Diversification and the 2007 Financial Crisis

By diversifying stock selection on an international basis, portfolio managers hope to improve the trade-off between risk and reward through a reduction in within-portfolio correlation levels. Although the benefits of this procedure can be considerable, the process of stock selection is not always clear cut. It was argued more than twenty years ago by French and Poterba (1991) that behavioral factors, such as biases in investor expectations, can lead to under-diversification in the international dimension. Portfolio managers wanting to optimize their stock selection can now be seen to face another important issue; namely, whether or not financial crisis results in significant long-term permanent changes in between-market correlation levels.