Market's ups-and-downs spell end of low volatility era

(Reuters) - In the last month, the U.S. stock market is down just 0.8 percent, but it's been a bumpy ride: Since Dec. 9, the S&P 500 has had a 4 percent selloff, a 6 percent rally, and a 4 percent drop that ended Thursday with a two-day gain of 3 percent.