<prompt> Human: Compound interest is the greatest force in the universe. -- Albert EinsteinAverage stock market returns are about 8. Or 7. Or maybe 6. Well, thats just a measly 1-2, right?I recently saw a commenter here on rpersonalfinance scoff at the idea that we not only encourage people to avoid consumer debt as much as possible, but we also emphasize low-cost, low-expense-ratio index funds and obsess over a measly 1-2 percentage points. I didnt reply, but let it knock around in my head until I had a proper way to express my thoughts.Id like to illustrate the power of a measly 1-2. A hypothetical single dollar invested at age 25, growing for 40 years in a tax-sheltered account, compounding annually at 8 interest, grows to 21.72. A single dollar invested the same way, but with 7 interest, grows to 14.97.A single dollar at 6 interest becomes 10.29.It doesnt matter if your return is knocked down a percentage point by a down market or expense ratios, its still down a point. You cant control the market -- but you can control expense ratios.So when we obsess over XYZ mutual funds expense ratio being 1.17 versus Vanguards 0.17, maybe you can see how measly 1 percentages add up when compounded over the span of your investing career.  <response>: Accounting for, say, 2 inflation, you can then describe those values as...8 for 40 years 9.8 times inflation7 for 40 years 6.8 times inflation6 for 40 years 4.7 times inflation 