Gloomy tales <a href=" http://www.laughmom.com/essay-graduate-school/#column ">bibliography for online sources</a> They cited as an example a three-month period when a U.S.bank stock index fell 22.84 percent. They said a ProShares ETFmeant to double that index's inverse performance might have beenexpected to gain 45.68 percent, but instead fell 17.3 percent.