Indeed, the data show a pronounced decline in global inequality over the past few decades, driven largely by rising prosperity in poorer countries.

Misleading article. I'm fairly certain that 99% of people discussing the problems of inequality are referring to inequality within the developed world, not the inequality between developed countries and developing ones. Obviously a wealth tax would primarily affect the developed world.

Agreed! Inequality is the fact that 1% of people own 30% of the wealth. Those people are seen as a potential revenue source to pay for social programs.