So here are his calculations for the taxes each income level pays. What this economist measured here is the amount of taxes the members of these income groups paid TO the government minus the amount of money these people got back in the form of various government payments:

Bottom quintile: -301 percent
Second quintile: -42 percent
Middle quintile: -5 percent
Fourth quintile: 10 percent
Highest quintile: 22 percent
Top one percent: 28 percent

As Mankiw explains the bottom quintile of Americans are essentially receiving $3 in UNEARNED income from the taxpayers for every dollar they earn. He also points out something rather critical, and this is the fact that the middle quintile of taxpayers is in the negative, which means that they are net tax consumers. That is almost a 20 point swing since 1979, when middle income earners were tax contributors.

This explains how 50% of Americans pay no income taxes at all … and instead absorb tax money paid by others.