When investors are nervous, they flee risky assets like stocks for the safety of cash. That's exactly what's been happening lately. Since July 1, cash and money market funds have easily been the world's most popular asset class, attracting $208 billion of inflows, according to Bank of America Merrill Lynch. By comparison, investors have poured a relatively paltry $7 billion into stocks and yanked $46 billion from bonds. It's the latest evidence of the jitters ripping through financial markets amid crashing oil prices, a slowdown in China and soft U.S. economic activity. "The individual investor is scared by the volatility....