Short Sellers Sink Their Teeth Into ETFs

Bearish bets on ETFs have jumped to their highest levels since May 2007 with some 2 billion shares in various U.S.-listed ETFs currently sold short, Barron's reported, citing Ned Davis Research. And it's not just this year's laggards that are vulnerable to big short positions. Health care ETFs such as the iShares U.S. Health Care ETF

and the iShares Dow Jones U.S. Medical Devices ETF

have been solid performers this year, but this ETF genre is also home to massive short-selling as traders look to book profits. Nearly 26% of all health care ETFs' shares outstanding were sold short at the end of May, Barron's reported. Ned Davis research points out the iShares Silver Trust

had 33 million of its shares outstanding sold short. That's a hefty chunk of the ETF's 315.1 million shares outstanding. The picture is only marginally better for the SPDR Gold Shares

, which had about 23 million shares sold short as of the end of May, good for its highest level since May 2008, Barron's reported. GLD had 398.9 million shares outstanding as of Wednesday, according to the SPDR Web site. As Benzinga noted earlier this month, energy ETFs have also seen big jumps in short positions. The Energy Select Sector SPDR

saw short bets on that ETF jump 18% in May after a 16% increase in April while the SPDR S&P Oil & Gas Exploration & Production ETF

had 53 million shares sold short in it, or 3.5 times its total shares outstanding, at the end of last month.