At that income level, a married couple with two children and childcare expenses could easily end up with zero tax bill and maybe even paying negative income tax. Standard deductions, child tax credit and childcare expense credits get you there without any exceptional circumstances.
The average number of people per household is 2.6.
The two adult two child family is not a median american family. It's a much-larger than normal family. Of course if you apply their deductions to an average income, you get a very low tax rate.
