What is Home Bias?
Home bias describes investors' preference for domestic stocks over foreign ones. US investors hold roughly 80% of their equity allocation in US stocks, even though the US represents only about 60% of global stock market capitalization. Japanese investors are even more extreme, with domestic equities comprising over 85% of their stock holdings despite Japan representing only 6% of global markets. This overconcentration in a single country's economy creates unnecessary risk.
The Cost of Home Bias
From 2000 to 2009, the S&P 500 returned essentially 0% (the 'lost decade'), while international developed markets returned about 30% and emerging markets gained over 150%. A US-only investor missed a decade of global growth. Conversely, Japanese investors who held only domestic stocks from 1990 to 2012 suffered a 75% decline, while global diversification would have produced positive returns. Vanguard research estimates that optimal international allocation is 30-40% of equities for US investors and even higher for investors in smaller economies.
Key Considerations
Home bias persists because of familiarity preference, currency risk aversion, and information asymmetry - investors feel they understand domestic companies better. However, many large domestic companies already derive 40-60% of revenue from overseas, providing indirect international exposure. True diversification requires explicit international allocation. Currency hedging can reduce short-term volatility but costs 0.5-1.0% annually and eliminates the diversification benefit of currency exposure. For most long-term investors, unhedged international exposure of 25-40% of equities improves risk-adjusted returns.