Net sales of exchange-traded funds increased $1.7 billion, according to the monthly report from the Investment Company Institute.

The Nasdaq-100 Index Track Stock, known as its ticker symbol QQQ or Cubes for slang, accounted for a fair share of new money as investors bought $3 billion worth of shares as part of a short-selling strategy, said Avi Nachmany, who leads research at New York-based Strategic Insight. He said this wasn’t the first time the number of QQQ shares went up when the market went down.

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