Why the US is the only country where 47% of citizens don't pay an income tax

After Republican Presidential candidate Mitt Romney castigated the 47% of Americans who don’t pay income tax (largely because of tax breaks for the poor, students, elderly and veterans), WonkBook’s Dylan Matthews wondered if other developed economies experienced the same phenomenon. Turns out they don’t–and it raises questions about whether a progressive tax code is as effective as progressive government spending priorities.