I am pretty convinced that β>0, even though I also think there is some contribution to slowdown from other factors. Some reasons:
Bloom et al observe β>0 not only in the economy at large but in various subdomains, such as transistors and Moore’s Law. If you want to argue that this is all caused by society’s resistance to innovation (which is real), then you have to argue that society also resists innovation in integrated circuits (which… doesn’t seem like a thing).
There are simple intuitions for β>0 based on low-hanging fruit and burden of knowledge (both of which you mentioned).
Scott Alexander gives some intuition for why we should expect β>0 here; if it weren’t then progress would long ago have accelerated to insane levels. In fact, I haven’t checked the math, but I think if β=0 you end up with a hyperbolic curve where GDP goes infinite in finite time; see this other Alexander post (although the paper that post is based on is kind of silly and not written by an expert in the field; Kremer 1993 is a better reference for this idea and is worth reading).
That said, I am also pretty convinced that there is a contribution from institutions and other factors. (To paraphrase something Eli Dourado said to me, TFP growth is slow in Venezuela, and no one thinks that is because ideas are harder to find in Venezuela.)
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 am pretty convinced that β>0, even though I also think there is some contribution to slowdown from other factors. Some reasons:
Bloom et al observe β>0 not only in the economy at large but in various subdomains, such as transistors and Moore’s Law. If you want to argue that this is all caused by society’s resistance to innovation (which is real), then you have to argue that society also resists innovation in integrated circuits (which… doesn’t seem like a thing).
There are simple intuitions for β>0 based on low-hanging fruit and burden of knowledge (both of which you mentioned).
Scott Alexander gives some intuition for why we should expect β>0 here; if it weren’t then progress would long ago have accelerated to insane levels. In fact, I haven’t checked the math, but I think if β=0 you end up with a hyperbolic curve where GDP goes infinite in finite time; see this other Alexander post (although the paper that post is based on is kind of silly and not written by an expert in the field; Kremer 1993 is a better reference for this idea and is worth reading).
We arguably see similar patterns not only in technology and the economy but also in science and the arts. Holden Karnofsky makes an argument for this here.
That said, I am also pretty convinced that there is a contribution from institutions and other factors. (To paraphrase something Eli Dourado said to me, TFP growth is slow in Venezuela, and no one thinks that is because ideas are harder to find in Venezuela.)
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.