Only one word that should convince you about the need to diversify your investment portfolio globally: Japan.
Since 1990, we've lived through a 27-year stretch where Japanese large cap stocks (the equivalent of the S&P 500) have had a negative total return. Japanese investors who put all their money in their own home market haven't even gotten back what they started with a quarter century later. Over this period, every other region of the world has performed remarkably well. A globally diversified index portfolio compounded at +10.7% per year over this period (including its stake in Japan), and $1 grew to almost $16.
Of course, the odds that this happens to the US stock market are small. But why make the gamble?
Past performance is not a guarantee of future results. Index performance shown includes reinvestment of dividends and other earnings but does not reflect the deduction of investment advisory fees or other expenses except where noted. This content is provided for informational purposes and is not an offer, solicitation, recommendation or endorsement of any particular security, products, or services.