That's false. Firms have been spending more on expanding capex investment than stock buybacks. There's a capex boom going on with the S&P 500 right now.
Year over year capex growth was up 15.6% in the first quarter, and 18% in the second quarter.
By contrast, capex growth for the S&P 500 was flat to negative for most of the prior five years, and was negative for nine straight quarters prior to 3Q17.
We haven't seen that kind of capex boom since the initial bounce out of the great recession in late 2010-2011. And that was massively juiced by the Fed, whereas we're in a very different Fed environment now.
https://www.bloomberg.com/news/articles/2018-04-26/trump-tax...
Plus more recent news is this: https://www.marketwatch.com/story/capex-is-starting-to-ramp-...
This shows that capex investments are only starting to ramp up, are unevenly distributed.
In general it supports the position that stock buy backs are the preferred route of money use given the current monetary scenario. Especially since stock buy backs are at record highs.
This helped me find another point of interest - that 10% of households hold 86% of stocks. Meaning that the gains to shareholders will only re-concentrate wealth.
So The marginal choice is known - perhaps the easy wins to be won from human productivity increases have been achieved?