Households with an adjusted gross income (AGI) less than $50,000 comprised about 80% of all US households in 2012. So, I think your threshold is a little high.
If you were to choose $36,000 as your threshold instead, that was about the median household income in 2012. So, 50% of households had less, 50% of households had more.
If you look at the group with less than $36,000/year, their average individual income tax rate was 3.28% in 2012. So, they were very close to zero. The next 10% (50th to 60th percentile) paid as much income tax as the entire bottom 50%, despite earning only half as much total AGI.
That’s all? Only $50,000 household income in 2015?
Heck I made that all by myself in 1986.