I just did a quick scan of the book. Most references where the author includes dates are for 2006. So I suspect the data is from prior years. I did get an e-mail address for him from the purchasing agency. You might try the following:
ryanerisman@gmail.com
We're waiting for grandchildren to descend upon us so I'm biding time on the Web. Merry Christmas to all.
The Tinker (which is an Irish gypsy for those of you who might have wondered)