<prompt> Human: Do you think it is necessary to include international funds to your portfolio like an international index fund or do you agree with Collins in simple path to wealth that the international exposure provided by SP 500 index funds like VTSAX is enough? I know its important to diversify but international funds have higher expense ratios and are volatile.  <response>: We cant know what will be the best path going forward. For that reason I believe international diversification is important.The anti-international argument you cite is extremely common, but it seems to have a fatal flaw that few people who believe it are willing to accept; it expects that the future outcome is that the US market remains the dominant world market. So long as that happens, what they say is generally correct - many US companies have a global presence that helps diversify their earnings, and the fact that the US market is over 50 of the total world stock market means that the world market is likely to look a lot like the US market with more volatility.The problem is, what happens in a future where the US market is in long-term decline and no longer the major driving force? In a world where the US market is 10 of the market as a whole, it wont matter that major US-companies still derive profits from outside US borders. Without international diversification you will have missed out entirely on the new engines of growth, and suffered badly as the US market goes into extended decline. 