On explaining productivity -- a follow-up

Me:

Cobb-Douglas is a "production" function. A supply side function. Demand concepts like the Kaldor-Verdoorn Law are ignored. Schneider's "simple growth accounting decomposition" shows clearly that slow productivity is caused in part by slow technological growth and in part by capital shallowing. From this, one could conclude we need policies that boost tech growth and policies that enhance capital deepening. But to reach such conclusions without also considering the demand side would be a grave error.

In my notes just now, I came across this excerpt from 2016, from John Mauldin:

GDP growth has only two basic components: growth in productivity and growth in the workforce size. That’s it. There are two and only two ways you can grow an economy: increase the (working-age) population or productivity.

Therefore—and I'm oversimplifying quite a lot here—a recession is basically a decrease in production (as, normally, population doesn't decrease). Two clear implications emerge: The first is that if you want the economy to grow, there must be an economic environment that is friendly to increasing productivity.

Mauldin -- a very sharp guy -- leaps from a conclusion arising from growth accounting to a very specific conclusion about the policy needed to boost productivity. That leap is exactly the kind of grave error I had in mind.