However, short sales data indicate so many shares of TAN have been borrowed that it would take traders eight days to cover all those bearish bets, a number that has not been exceeded in 18 months, according to Schaeffer’s.

TAN is no stranger to heavy shorting. In fact, massive short bets on the ETF’s holdings have allowed the fund to consistently outpace its underlying index while offering a decent dividend yield, an uncommon trait in the world of solar stocks, due to a profitable securities lending plan implemented by Guggenheim. [Solar ETF’s Secret Sauce]

Speaking of short sales, TAN constituents including First Solar, Solar City, GT Advanced Technologies (NasdaqGS: GTAT) and SunEdison (NYSE: SUNE), have been among this year’s most heavily shorted issues. Those stocks combine for 29.4% of TAN’s weight, according to Guggenheim data.

Guggenheim Solar ETF