This is a little outside our usual purview, but the research is interesting and topical. Any day now, there won't be a (non-adult) bookstore within walking distance of AdAgeStat HQ, despite working in the heart of one of the largest metro areas in the nation.
GfK MRI dug into its Survey of the National Consumer data and found that 13.8% of adult book shoppers said they shopped at Barnes & Noble, but not Borders. Only 5.5% said they shopped only at Borders. Still, that represents 12.5 million book shoppers who now seem likely candidates to become Barnes & Nobel shoppers, assuming there's a B&N handy, which would not be the case at HQ.
One thing that B&N will have going for it is a similar customer base. The Borders customer looks a lot like the B&N customer: leaning liberal and upper-income, Walmart and Target shoppers, and brand-loyal.
So as long as Amazon doesn't suck up all of the Borders customers, this could be an easy win for B&N.