I have noticed that US retirement funds generally seem to allocate far more space to US stock than international (non-US) stock. Of course, there is not really any such thing as a prototypical retirement fund, but this is what I see when I look at target date funds by major US mutual fund vendors, which seems as close to a "typical" retirement fund as anything.
For example, Vanguard's Target Retirement 2050 Fund (VFIFX) currently allocates 62.1% to VTSMX (US equities) but only 27.9% to VGTSX (international equities). Fidelity's Freedom 2050 Fund (FFFHX) currently allocates 65.42% to various domestic equities but only 27.56% to international equities. As of Dec 31, 2014, Charles Schwab's Managed Retirement Trust Fund 2050 allocated 67.27% to various domestic equities but only 21.46% to international equities. Roughly the same proportions hold for the fixed-income/bond parts of those funds.
Why is so much more asset space allocated to US assets? The US is certainly a major economy (GDP about 16 trillion), but it's nowhere near two-thirds of the global economy (which is somewhere above 60 trillion, it appears). Would vendors based in other countries allocate a similarly large amount of space to assets from their own countries? That is, would a vendor in, for example, Brazil allocate a larger amount of asset space to Brazilian equities/bonds? If so, why?