A centralized scheme of world redistribution that maximizes a border-neutral social welfare function, subject to the disincentive effects it would create, generates a drastic reduction in world consumption inequality, dropping the Gini coefficient from 0.69 to 0.25. In contrast, an optimal decentralized (i.e., with no cross-country transfers) redistribution has a miniscule effect on world income inequality. Thus, the traditional public finance concern about the excess burden of redistribution cannot explain why there is so little world redistribution.
Actual foreign aid is vastly lower than the transfers under the simulated world income tax, suggesting that voluntary world transfers—subject to a free-rider problem—produces an outcome that is consistent with rich countries such as the United States either placing a much lower value on the welfare of foreigners, or else expecting that a very significant fraction of cross-border transfers is wasted. The product of the welfare weight and one minus the share of transfers that are wasted constitutes the implicit weight that the United States assigns to foreigners. We calculate that value to be as low as 1/2000 of the value put on the welfare of an American, suggesting that U.S. policy is consistent with social preferences that place essentially no value on the welfare of the citizens of the poorest countries, or that implicitly assumes that essentially all transfers are wasted.
Somewhat related:
The Limitations of Decentralized World Redistribution: An Optimal Taxation Approach