 The CBOE Volatility Index and VIX-related exchange traded funds surged Tuesday as weak retail sales data fueled fears that the economic recovery may be unraveling. Among the best-performing non-leveraged ETFs of Tuesday, the iPath Series B SP 500 VIX Short Term Futures ETN NYSEArca: VXX increased 5.4 and the ProShares VIX Short-Term Futures ETF NYSEArca: VIXY . 