Selling on the NYSE on Tuesday afternoon has reached panic-like proportions, as the exchange's Arms Index rose. The Arms is a volume-weighted breadth measure, that tends to rise when the broader market falls, as the intensity of the selling in declining stocks is usually greater than the intensity of buying in rising stocks. Values above 2.000 are considered panic-like activity. The NYSE ARMS index showed 2,507 decliners for 445 advancers and was at 2.497, according to FactSet data. So far, selling has been broad based, with the the Dow Jones Industrial Average DJIA, -1.90% trading 775 points, or 3%, lower, and threatening to notch its worst day since March 22. Meanwhile, the S&P 500 index SPX, -2.24% was down 3.7% at 2,702, while the Nasdaq Composite Index COMP, -2.86% was down 3.8% at 7,165.