> ...this means that only 20% of labor productivity growth in the US since 1988 has been driven by R&D spending! Capital deepening accounts for around half of labor productivity growth in this period...
This is like saying that Jeff Dean's net worth is attributable not to his programming skills, but to the capital deepening of his bank account. The authors are working with concepts at a level of abstraction where they've lost contact with what they're saying.