I basically agree with everything you’ve said here.
On the subdomains point, you can have decreasing returns within each subdomain but constant returns overall if you keep finding new subdomains. I think this is an accurate model of progress. It captures ideas like paradigm shifts and also integrates the intuitions for low-hanging fruit and burden of knowledge in a way which still allows rapid progress. My favorite example is the Copernican revolution. There were huge obstacles from burden of knowledge and low-hanging fruit in Ptolemaic astronomy. It took so much extra data and education to improve the epicycles of Mercury by a few decimal points. But once astronomy moved to a new model, there was a whole new grove of low hanging fruit and almost none of the investment in Ptolemaic astronomy was necessary to make progress so the burden of knowledge was reset.
Absolutely true that new subdomains open up new areas of low-hanging fruit. It is the “stacked S-curve” model.
Not immediately clear whether what this means for β>0. I think this model may be addressed in Bloom et al, or maybe in an earlier paper by Jones. I vaguely recall that it doesn’t make a difference whether you analyze things in terms of the subdomains or the economy at large, but I don’t have the exact reference at hand.
I basically agree with everything you’ve said here.
On the subdomains point, you can have decreasing returns within each subdomain but constant returns overall if you keep finding new subdomains. I think this is an accurate model of progress. It captures ideas like paradigm shifts and also integrates the intuitions for low-hanging fruit and burden of knowledge in a way which still allows rapid progress. My favorite example is the Copernican revolution. There were huge obstacles from burden of knowledge and low-hanging fruit in Ptolemaic astronomy. It took so much extra data and education to improve the epicycles of Mercury by a few decimal points. But once astronomy moved to a new model, there was a whole new grove of low hanging fruit and almost none of the investment in Ptolemaic astronomy was necessary to make progress so the burden of knowledge was reset.
Absolutely true that new subdomains open up new areas of low-hanging fruit. It is the “stacked S-curve” model.
Not immediately clear whether what this means for β>0. I think this model may be addressed in Bloom et al, or maybe in an earlier paper by Jones. I vaguely recall that it doesn’t make a difference whether you analyze things in terms of the subdomains or the economy at large, but I don’t have the exact reference at hand.