I'm well aware of inflation being far higher than 3.5 percent across much of the West. The reason I used 3.5 percent was two-fold.

First, over the long run, US inflation averaged around 3.5 percent. This includes periods of inflation higher than its current rate. When calculating for a multi-decade period, it would have been unreasonable to assume a much higher rate.

Second, to show that even at such a reasonable rate, over a person's investing career, inflation eats at our money's purchasing power far more than people think.