Stocks witnessed one of the most volatile days of trade ever, with the Nifty swinging nearly 400 points, or 3.6 per cent, on Monday. The 50 stocks in the index gyrated an average 5.7 per cent. The previous instance of such a wild swing was on September 19, when the indices reacted to the surprise cut in corporation tax. YES Bank swung 16.2 per cent, the most among Nifty components, followed by SBI, which moved almost 9 per cent. The India VIX, a gauge for market volatility, touched a low of 19.92 and a high of 26.34 — a move of 32 per cent.