What's Up with Turkmenistan?

Via Matt Yglesias, Gallup has a global survey of nations which are thriving, struggling, or suffering.  It's color-coded.  Briefly US, Canada, UK, and Scandinavia are thriving, the rest of the world not so much.  But Turkmenistan sticks out like a sore thumb in having a higher score than any country within thousands of miles of it.  What's that about?