The real rate of return is the total return earned by an investment after subtracting taxes and other fees and accounting for inflation.
If a gold coin was purchased for 100 USD and sold for 110 USD the nominal rate of return was 10%, but the real rate of return was likely much lower. For example, assume 5 USD was paid to ship the coin (a fee), 2 USD was paid in taxes on the "profit" and inflation was 3%. In this case the real rate of return was 0%.
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