The NASCAR Sprint Cup Series' biggest movers and losers in 2009

Plus or minus. Statistically speaking, it's one way to look at how much a driver has improved, or not improved, from the previous season.After 31 of 36 races in 2009, it's a good time to see who moved up or down the most from a year ago. To be fair, we need to compare relatively equal circumstances, so guys like Tony Stewart, Ryan Newman, Mark Martin and Casey Mears don't really fit on our plus-minus scale.So who's the big winner? At a plus-13, it's Kurt Busch. He finished 18th in the 2008...