From The Passive Voice: http://www.thepassivevoice.com/03/2013/bookshop-browsing-vital-for-publishing-research-finds/
"The single most effective technique for dismantling the physical book sector would be to accelerate the closure of bookshops," said McCabe. "We estimate that when a bookshop closes, about a third of its sales transfer to another bookshop. This means as much as two-thirds of sales disappear. Some of this spend doubtless migrates online, but much of it vanishes from the book sector entirely."
However, the research showed a higher number of books being bought from internet-only businesses than from bricks-and-mortar stores for the first time in 2012.