The closed below its 50-day moving average on Wednesday, its first time under that widely watched indicator since Election Day, which has some chart analysts worried the bullish trend put in place since President Donald Trump's win is reversing.
The historical data shows there is reason for concern.
S&P 500, 6 months with 50-day moving average:
Using hedge fund analystics tool Kensho, CNBC analyzed 245 occasions when the S&P 500 closed below its 50-day moving average since 1990. A week later, the stock benchmark was lower by 1 percent, on average, while bonds and gold were in the green.
A month later, the results were much of the same, according to Kensho, with the S&P 500 lower and gold and bonds higher.
Looking a little further out, things start to recover. The S&P 500 is up by 1.14 percent, on average, six months after a 50-day negative breach.
Bottom line: History shows Wednesday's weak close is cause for short-term concern.
Disclosure: NBCUniversal, parent of CNBC, is a minority investor in Kensho.