"Many behavioral psychology studies have shown that even when your life is improving in absolute terms, you see very little psychological benefit when your life isn’t improving as quickly as your neighbor. Your absolute size of the pie is less important than your relative slice of the pie (Christian Elger and Armin Falk — University of Bonn). This is why inequality is so damaging to the national psyche. The video below shows one monkey becoming irate as his neighbor receives more for the same work. Humans are not monkeys, but we share similar psychological patterns."