Probably a silly question but according to this backtest...
Beginning of 2007 SPY is at 72.01%,
Beginning of 2008 SPY is at 78.66%
Beginning of 2009 SPY is at 13.95%
But the draw down SPY between 2008-2009 was less than 2009s beginning % subtracted from 2008s beginning %. Why is that?