Key Points The S&P 500 is on pace to generate double-digit gains for a third consecutive year. Some investors are worried that the stock market is in a bubble. History shows that investing during market downturns is a profitable idea in the long run. 10 stocks we like better than S&P 500 Index › With only a handful of trading days left in the year, it's looking like the S&P 500 (SNPINDEX: ^GSPC) will post double-digit gains for the third year in a row. As of mid-day trading on Dec. 19, the S&P 50 ...