It’s also obviously untrue given the fact that wages in the US have stagnated while productivity has continued to grow. That’s despite a floor on wages.
However, the middle class has shrunk quite a bit as the upper middle class has seen tremendous growth while lower middle and poverty classes have seen a good deal of shrinkage.
37% today are lower-middle or poverty class compared with 50 years ago where 48% were. In particular, the poor have shrunk from 24% to 20% today.
So the middle and upper-middle have grown over the last 50 years with the upper-middle in particular growing and lower-middle and poverty has shrunk. However, middle class people may feel left behind as they see more people becoming upper-middle.
[1] https://www.urban.org/sites/default/files/publication/81581/...
What does capital produce?
But that's not completely true, because a person who only knows how to dig with their hands still only digs one hole a day, even if there's a shovel just lying there. Knowing how to use the tools does in fact make you a more productive worker.
It seems to me, then, that part of the gain from the productivity from better tools should go to the worker who knows how to use the tools. And part should go to the person who bought the tools.
This is why Adam Smith, for example, cites labour as the primary factor of production, followed by land with capital as the last. In modern parlance you might hear that said as "human capital is the most important", but human capital really is a politically correct way of saying "labour potential".
> Textbooks state that, in the absence of a minimum wage, a worker is paid his “marginal product of labour”, which means the value of what he produces.
You may disagree with my reasoning, but you yourself are making the case that workers are not paid for the value of what they produce.