How much of my stock allocation should be international?

There's no single right answer, but most evidence points to holding meaningfully more international stock than U.S. investors typically do. International companies make up roughly 40% of global market value, yet many Americans hold almost none — a home-country bias driven by familiarity, not logic. Common guidance lands between 20% and 40% of your stock allocation in international (developed and emerging markets combined); a total-international index fund captures it cheaply. Diversifying abroad protects you when U.S. stocks underperform, as they have for long stretches historically, and smooths returns over decades. The downside is short-term currency swings and stretches where the U.S. leads, which can test your patience. Pick a percentage you can hold through both, write it down, and stop tinkering. A three-fund portfolio naturally builds this in via its total-international fund.