Koji,
I don't know, but I am pretty sure all those were quoted in gross terms meaning simple conversion using Forex exchange rate. As for China and India,
I used a conversion ratio of 5 because China's gross gdp is around $1.3 trillion and gdp in ppp terms is around $6 trillion.
I guess what your source says about "using ppp for developing markets" is because these countries, china, russia, india, etc, do not disclose these
info readily so the US has to make a guess.
Does anyone else know how to explain this issue?