The fixed ratio is baseless. He's implicitly assuming two things, both incorrect:

1. A fixed capital-labour ratio in all sectors and professions over time.

2. Constant total factor productivity (a proxy for technical change and the efficiency of use of factors of production-- capital, labour, natural resources, institutions, etc.) universally across industries and geographies.

As a counter example on the first, do we believe that the capital intensity of the development of biologics by doctoral biochemists requires the same capital intensity as the work of university professors of literature with doctorates, always and everywhere?

On the latter, should we believe that productivity changes in the automotive industry in New Dehli are the same as in the southern US, and eternally so?

What is to give light must endure burning.