The S&P 500 was recently trading down 24.44 at 979.65.
From
Bespoke Investment Group (I love their simple little charts):
...As shown in the chart below, 946 is where the index's 50-day moving average currently stands, and it was also the index's high level in late May. If the S&P does head down to the 946 support level, it would be a decline of about 3.5% from here.