When it comes to exchange rates, I prefer to digest mine as burgernomics:

http://www.economist.com/markets/Bigmac/Index.cfm

According to Big Mac theory, the yen's fair value is around 82 to the dollar, so at 122:1, it was considered 33% undervalued -- the world's most undervalued currency, at that. A reversal has been long overdue, and while I don't think we'll see 82:1 anytime soon (unless the dollar really collapses!), it's worth remembering that it's only been a little over two years since the yen was almost at 100:1...