Grexit uncertainty. In the summer of 2015, Greece’s ability to pay its debt was so uncertain that it was considering leaving the eurozone and reverting to using the drachma as currency. Most Americans had little to no exposure to Greek equities or bonds, but nevertheless, the S&P 500 index (all U.S. companies, by the way) dropped by almost 7 percent in August 2015, when this news was going on. In a happy outcome to this story, just this summer Greece completed austerity measures to restore economic growth – and the eurozone was able to end its financial bailout of Greece. However, even if a Grexit-type scenario had occurred, would this really affect global market fundamentals?
Ebola. In the summer of 2014 markets were seriously spooked by the very real ebola crisis. From a market standpoint, realistically this would only affect biotech and health stocks to some degree. However, the entire S&P 500 dropped by more than 9 percent from Sept. 19, 2014, to Oct. 15, 2014.
Flash crash. Spoofing algorithms caused the prices of several large exchange-traded funds to become unhinged from their true value. Investors saw nearly $1 trillion of value erased from U.S. stocks in just 15 minutes, with the Dow Jones industrial average falling.