There are places where you get 5-10% interests on fixed deposits (mostly Asian countries). At approx 7%, you can double your money in 10 years. At 10%, you can double in 7 years approx and so on. It all depends on where one is living, I suppose. I can't find anything in the US market though - bank interest rates are a joke, treasury/bond % is too low. Stock market is on fire, but most stocks are so expensive that it is out of reach for most Americans.

I am not sure what other choices Americans have ...