Statistically speaking, the worst might not be over for the global economy.

A new study by the International Monetary Fund looks at 147 banking crises since 1970 and found that they most frequently began during the last six months of the year. The huge spike in September is largely explained by the financial collapse of 2008, says Luc Laeven, who co-authored the study. But even if you take out 2008, he says, "about two-thirds of the crises start during the second part of the year, with large end-of-summer and end-of-year effects."

I asked Laevan what might account for the trend. "I really don’t know," he replied. But he pointed out that, historically speaking, September is also the worst month for the S&P 500.