There has been a lot of discussion lately regarding the surge in volatile late-day trading that has occurred since the summer sell-off and fall credit-crisis began to unfold. In November alone, an average of 26.2 percent of trading volume in S&P 500 stocks took place in the final hour of trading, with 17.1 percent of the trading occurring in the final 30 minutes (see WSJ article). Furthermore, for eight of the ten worst days for the S&P 500 since September 1st of this year, 29 percent or more of the move took place in the final hour of trading, with three instances in which over half of the market decline occurred during the last hour. Much of the blame for the late day sell-offs has been assigned to hedge fund redemption selling, or simply nervous traders unwilling to hold positions overnight. A possible new culprit may be ETFs, in particular, leveraged ETFs.

Leveraged ETFs, now numbering over 100 in total (see lists here and here), have recently become popular since they allow market participants to take 2X and 3X positions on popular stock and sector indexes. Many of the leverage ETFs utilize swaps and options to achieve their leverage ratios. Not surprising, when the linked index or sector falls, corresponding stocks in the ETF have to be sold at a two to three times greater rate, increasing the moves in the indexes. In fact, the trend has become so predictable that many proprietary trading desks actively trade the levered ETFs toward the end of trading days with large moves, knowing that increased buying or selling is on its way. While the VIX has been coming down over the last few weeks, it is still at elevated levels, indicating that the next big daily move up or down is likely to be capped off with an equally impressive last hour move, generated in part by momentum investors taking a position in leveraged ETFs. For once, the market (myself included) has someone else to blame besides the hedge funds for late day trading volatility.