For 30 years, my calculation says 7.17%, which just doesn't seem right.

Say you invest $1 each year for 30 years with a return of investment of 7.17%

Total investment from your end = $ 3

Total return you get: $(((1 * 1.0717) + 1) * 1.0717) + 1) * 1.0717.... 30 times (Sum of GP) = $ 97.4

Now a 4% inflation rate, over 30 years, $1 will equal: 1.04^30 = $3.24

Effectively your money will amount to: $(97.4) / 3.24 = $ 30.06

Which is exactly how much you invested. I'm just wondering if my maths and/or economics is wrong or do I really need 7.17% roi just to maintain my money?


You’re not deflating your $1 investments in future years by the rate of inflation. Your total investment over the 30 years is a lot less than $30 at today’s values. Pretty obviously (ignoring tax and management fees), you need a 4% return to keep up with 4% inflation.

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