Use much larger international samples, including data from markets that shut down or had long interruptions. Doing this brings the return down several percent from the USA estimates; for example, Jorion 2003.
(It stands to reason that to maximally avoid survivorship bias and diversify, you would want to invest equally in every country, at which point your portfolio would grow something like the growth rate of the global economy which is ~2% annually over the last century or two IIRC; ironically, this apparently has happened to the Norwegian sovereign wealth fund—it’s too big to invest significantly in any particular market, so they are ultra-diversified and have what looks like low annual returns.)
Long run (as in, 100 years on NYE) returns on the stock market are more like 9-10% if you re-invest dividends.
You might want to wait till you have a taxable income to claim deductions on.
Despite these two considerations, I agree with donating subtantially at present (and do so myself).
Survivorship bias: US stock markets did much better than the world average, with many markets stagnant or outright expropriated.
Do we know how to control for that, quantitatively?
Use much larger international samples, including data from markets that shut down or had long interruptions. Doing this brings the return down several percent from the USA estimates; for example, Jorion 2003.
(It stands to reason that to maximally avoid survivorship bias and diversify, you would want to invest equally in every country, at which point your portfolio would grow something like the growth rate of the global economy which is ~2% annually over the last century or two IIRC; ironically, this apparently has happened to the Norwegian sovereign wealth fund—it’s too big to invest significantly in any particular market, so they are ultra-diversified and have what looks like low annual returns.)