It's Hard to Estimate Russian GDP

Marginal Revolution gives some evidence on why I am skeptical that Russian GDP went down after reforms:

Andrew Gelman has a simple question, What is Russia's GDP per capita?  Fortunately this information is easy to find on the web.  As Gelman reports, the answer is:

   1. $7,600 (World Bank 2007)
   2. $9,100 (World Bank 2007)
   3. $14,700 (PPP adjusted, World Bank 2007)
   4. $4,500 (World Bank 2006)
   5. $7600 or $14,400 (gross national income: "Atlas method" or "purchasing power parity," World Bank 2007)
   6. $12,600 (IMF 2008), $9,100 (World Bank 2007), or $12,500 (CIA 2008)
   7. $2,637 in 2000 US dollars (World Bank 2007); that's $3,200 in 2007 dollars
   8. $2,621 (World Bank 2006) or $8,600 (IMF)