I understand why a stock going into or out of a Russell Index on the upcoming rebalance day would have a volume surge, especially on the close. But for stocks staying in the Russell 2000, there still seems to be a big surge, even for stocks that have not moved much during the previous year (e.g. TTEC on June 24, 2016, which looks like it traded 67K shares on the close vs 6K the previous day). Any idea why this occurs? And, less important, is the volume spike magnified for stocks that have gone up or down a lot in the previous year? Thanks.