Long-term Treasury securities have outperformed the Standard & Poor's 500 stock index for the past 10 years. The SPDR S&P 500 ETF has gained an average 7.27% over the past decade, according to Morningstar Inc., but the iShares 20+ Year Treasury Bond ETF has gained an average 9.31% during the same period. From a very long-term historical perspective, this is an anomaly. Read the original story from InvestmentNews.