Ken French says that, while home bias is still the norm, investors have significantly increased their allocation to foreign markets over the last 30 years. He explains that investors might overweight their home market for economic reasons, perhaps to hedge consumption risk or to offset tax disadvantages they suffer in some foreign markets. Home bias can also be driven by behavioral factors. For example, investors may overweight their home country because of their uncertainty (the unknown unknowns) about foreign markets, or because they are overconfident about picking stocks in their home market. Ken says the best approach is to start with a global market portfolio, then make adjustments based on personal preference.