Visualizing Risk Standard deviations may be a very precise and technically correct way to describe risk, but I don't find it very intuitive. If we look at the pattern of returns in individual markets, we can perhaps get a much more visual and intuitive feeling for risk and reward. Treasury Bills have low returns and little risk. As you already know, T-Bills have never had a loss, but don't earn enough to provide meaningful real returns. Long-term Treasury Bonds have displayed a surprising amount of volatility as interest rates change.
Commercial bonds show some increased risk, but still have disappointing returns.