During the short nine days of trading from late January to February 8, the S&P 500 fell like a skydiver leaping out of a plane: fast and down. In a classic flight-to-quality response, investors pulled their parachutes, socking billions into the largest ETFs tracking the widely-watched Bloomberg Barclays U.S. Aggregate Bond Index (the “Barclays Aggregate”). This time, though, it didn’t work.