(Bloomberg) -- Love ETFs or hate them, one thing is clear: the biggest investors are increasingly using them as a way to dabble in inefficient and opaque bond markets.

Harvard Management, for example, sold about $90 million of shares in two junk-bond ETFs, some of its largest reported trades in the three months ended June 30. Two of the top three equity holdings reported by hedge-fund firm Tudor Investment were in corporate-bond ETFs, according to an Aug. 14 filing outlining positions as of June 30.

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