The High Yield 10 approach is easy, stable, and has been backtested an impressive 69 years. Using rolling 10-year periods is a much more informative way to look at the data. Well, its returns are relatively stable compared to most other investment strategies. To illustrate stability we need to talk about the dreaded standard deviation. I will try to make this as painless as possible.
Standard deviation measures the variability of a set of numbers.
Think of it as the Insomnia Index. You may already be guessing that the High Yield 10 has a nice, low standard deviation, but it's even better than that. Yes, it has beaten the market AND caused investors fewer sleepless nights. So that's what's good about it. If this super-safe strategy appeals to you, though, do consider using one of the less expensive brokerages.