This is basically a prisoner dilemma on a global scale where the incentives are for single marginalised nations to leverage the fact of being tax havens to survive globalisation. The dream of a single global tax is as possible as making China/US respect any of the agreements they have signed regarding trade and environment.

The same proposal is also criticized by many economists too, who argue that inequality has not risen as sharply as Piketty's crew claims, or that the bulk of that inequality is linked to the real estate, for which the only solution is build more houses and destroy the capital accumulation of older generation to the profit on newer ones.

1: https://www.brookings.edu/articles/deciphering-the-fall-and-...