Are US textbooks more expensive?

Hey Class,

So today we talked about the Purchasing Power Parity Theory, and the Law of one Price. My co-authors and I wrote a paper on price discrimination across countries in the book publishing industry. It is techically an easy-to-read paper, so if you are interested more about the subject you may have a look here: http://ssrn.com/abstract=807705

Here's the abstract:
We investigate differences in book prices between the United States and other countries. We find that general audience books are similarly priced internationally, but textbooks are substantially more expensive in the United States (often more than double the price). This disparity is much more pronounced for commercial publishers than for university presses. We argue that supply-side factors like cost and market structure can not explain this phenomenon. We discuss several demand-side explanations; our preferred theory is that higher US textbook prices reflect the unique status of the textbook as a centerpiece of US college instruction.