The math is so complex they could not draw any conclusions.
Understand; we listened to lesser educated men of the previous generation about building business and economy. Men who missed out on our early education in science, and who were often far more religious. Men who had much different political narratives to satisfy; IBM was gifted government research. How many of our startups are?
Brookings conveniently avoids discussing the weakening political power of the US over the decades; easy to grow when the world needs you to manufacture for it after WW2.
It’s not hard for me to believe much of our economic theory is bullshit, and output is driven by political arrangements. Humans will generate economic activity naturally to survive. One can only induce so much superfluous activity beyond that.
Humans have a history of ignorantly extrapolating the wrong conclusions from reality.