https://reprog.wordpress.com/2010/11...ork-in-the-uk/
From a brief search, it seems working round UK/US restrictions is not trivial. Also it appears to be impracticle to repeatedly switch between the two. In addition, the workarounds seem to awkward for most users. As such, it seems unlikely that the currency shift can explain the authorearnings downshift in US ebook earnings. I believe their data to be valid. Indie ebook sales in the US began to drop in May 2016. Why?