You have a math error.
A higher percentage rate of 1/10 the income, doesn't mean they have more to invest. In fact, food is stilll 30% of their budget. And as always the savings is power-law distributed and most of the people in the developing world have very little savings because they can barely meet their basic consumption expenses (and they've gotten a taste of materialism and spend to join the lifestyle of westerners).
No I don't have an error. I'd bet an average Chinese has more to invest than an average American. This works on both personal and on a country level. Who is the largest debtor nation of the world? Who is the largest creditor nation of the world?