You're right -- 12.25 is nominal, not inflation-adjusted. But inflation was in the range of 1.5-2%, so even adjusted for inflation, the real return exceeds 10%

You're right -- 12.25 is nominal, not inflation-adjusted. But inflation was in the range of 1.5-2%, so even adjusted for inflation, the real return exceeds 10% any way to slice it. I'm not sure what your calculator is measuring -- the date selection has a precision of one month. But swings of 5% in a month are common, so I would not immediately discount the idea that there are endpoint dates you could choose to get a 17% return.