The Bubble Index: SP500 – August 13, 2013 August 23, 2013 lpplmarketwatch standard and poors, united states The S&P shows no indication of a instability. However, the 1260 day graph does show that the index is now approaching its long term average of approximately 20 and shows no sign of decreasing. The Bubble Index: S&P 500 – 08_13_13