Lazaro: I'm not sure purchase zetia online While this is down from the record high of almost 20pc a year ago, the shares are still by far the most shorted in the FTSE 100 index. The next most borrowed is Aggreko, with 8.5pc, and G4S with 6.4pc of their shares on loan respectively, according to Markit. This means that some of yesterday’s gain is likely to be caused by a “short squeeze” as investors who had sold the shares expecting a fall bought them back.