Standard deviation of what, wealth? Income? You're on the right track though, at minimum you need to use something like purschasing power parity (PPP) to accou

Standard deviation of what, wealth? Income? You're on the right track though, at minimum you need to use something like purschasing power parity (PPP) to account for some effects, and wealth distribution to account for others. Doing these comparisons meaningfully isn't easy to get right.