Coinspeaker Stocks Plunge, S&P 500 Faces Worst September since 2011: What’s Up on Market?On Friday, the S&P 500 index closed 1.12% or 37.54 points down, at 3,319.47. The close was below S&P 500's 50-day moving average for the first time since April. At the moment of writing, it is even lower, at 3264.41. Stocks Plunge, S&P 500 Faces Worst September since 2011: What’s Up on Market?