The iShares Select Dividend ETF (NYSEArca: DVY) also experienced a quick turnaround in assets after enjoying a $17 billion injection before seeing the money funnel right back out two days later.

Ben Johnson, head of global ETF research for Morningstar Inc., explained that this typically occurs when ETFs rebalance their portfolios to realign holdings with their benchmark indices.

“There was a wholesale change to the underlying index methodology, so to implement that, they had to give the portfolio an extreme makeover,” Johnson told the WSJ.

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