Last year, ETF closures hit record numbers according to Deborah Fuhr at London based ETFGI, an independent research and consulting firm.

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In terms of cost differentiation between duplicate funds, Fuhr said investors need to be careful in understanding that often annual costs are adjusted based on level of assets in the fund.

FORBES: In ETF Space, Not Easy Fending Off The Copy Cats

"ETFs have really won people over, " Ms. Fuhr said.

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