Stocks had a great first half of September, but the tide is turning towards the end of the month.
Since Sept. 14, the S&P 500 index has given back over half of its gains, up about 2 percent so far this month.
On Wednesday, the S&P 500 closed down for the fifth consecutive session, down 1.9 percent in that period (the Dow Jones Industrial Average has closed down for four straight days, three for the Nasdaq Composite Index).
The current losses in the second half of September are not new to the market.
During the last 20 years, the first half of September has outperformed the second half of the month 75 percent of the time (highlighted in green below).