Pilots often describe their jobs as long periods of boredom punctuated by moments of sheer terror. Financial markets may seem disturbingly similar. Over the past few years, we have enjoyed a period of low volatility driven by central bank monetary policy. So, when volatility spikes, it seems unusual – even though it’s not. Long-term data shows that the average daily volatility of the S&P 500 index is around 0.7 percent and that this commonly doubles when significant events occur. Herding behavior in illiquid markets can exacerbate the trend. During the last few weeks, I’ve heard explanations for recent market volatility based on everything from slowing growth in China to panic over a potential Ebola epidemic.