It is also explicitly another prediction Marx made about capitalism: That the most successful (read: surviving) companies eventually by necessity will start to squeeze wages as the barriers to further expansion increases (that is, the population and disposable income does not grow fast enough to provide sufficient increases in profit) - those who don't will be unable to compete with those who do.

Marx believed that the end-stage of capitalism would be when increasingly profit comes by driving wages back down instead of expanding the overall market, and that the result will be a reversal of the gains made by the working classes at the same time as increased production, resulting in increased poverty and overproduction as the working classes can eventually afford fewer products.

This resembles Marx's theory of Surplus Value. This is evidence for Marx's theory of Surplus Value.

I still doubt the theory, but yes, it's valid evidence.

Just don't jump onver a conclusion too fast, because it's still evidence for substitution of production factors (that leads to competition between them), an idea almost completely opost to the labor theory of value. (Did I already tell you that I hate economics?)