You are right that Russia has not enjoyed a 31% compounded GEOMETRIC average return, but as I mentioned in the table it is average annual return. Russia actually had about a 8.3% compounded geometric annualized return from 1995-2017. What leads to the discrepancy? The huge volatility drag of 50% standard deviation with the best year having 246% return and worst year of -83% with 6 years lossing more than 20%.