Charts from the census data haul
Oh, it's shrinking, right into the upper class. Terrible that, we are becoming wealthier, and wealthier. It is becoming more, and more difficult for the doomsayers to stick to the script. The lower class is shrinking into the middle class, the middle class into the wealthy class. Thank the free markets for that shift.
Anyone who was alive 40 or 50 years ago, and who has a reasonably functioning memory is sure to tell you how much more difficult life was back then, in the dark ages, because it was.
This chart shows how much wealthy has been transferring downwards. This is what the free markets do, they empower the poorer, and make available to them the things only the wealthy had a few years ago. Socialism is not an alternative to this system, as it only dissipates wealth, it does not create wealth. Socialism, and its less authoritarian sister progressivism are envious ideologies, always seeing to spend others wealth as their own.
Our government driven welfare system makes the lower income category sticky, trapping more people than necessary in this low income zone. We need to reform welfare, break these sticky bonds, and free the poor to become wealthy. It is the moral thing to do.
An election is imminent, you will need to choose between these systems, choose wisely.