Recombinant Growth

I'm going to do something I normally hate doing and that's comment on something I haven't read.

Tyler Cowen has an e-book out arguing American technological progress has plateaued. From the description:

In a figurative sense, the American economy has enjoyed lots of low-hanging fruit since at least the seventeenth century: free land; immigrant labor; and powerful new technologies. Yet during the last forty years, that low-hanging fruit started disappearing and we started pretending it was still there. We have failed to recognize that we are at a technological plateau and the trees are barer than we would like to think.

Arnold Kling notes the irony that an argument about plateaued grow is coming in the form of a digital book for only $4. Of course you could argue that this constitutes "cutting edge" is a point in favor of Cowen's argument.

Based on my educated guess, Cowen's making an increasing marginal cost claim: as you pick the low hanging fruit, you're forced to climb the tree and go after the stuff that's harder to get. I use the same analogy when I teach principles. It works great for basic stuff like picking apples. But new technology is another story.

In a great 1998 paper, Martin Weitzman argues that knowledge causes "recombinant growth," or growth that builds on itself as ideas combine with other ideas. "The paper's main theme is that the ultimate limits to growth lie not so much in our ability to generate new ideas as in our ability to process an abundance of potentially new ideas into usable form."

It's not that we make technology, enjoy the benefits, and start again where we were. If it was, then we would have fallen back into gut-wrenching poverty long ago. The ideas we gain (not to mention the immigrants who help make those ideas) stay with use, which we use to make yet more ideas. These ideas combine with other ideas and make cutting edge stuff easier to achieve than our ancestors ever thought possible. High-hanging fruit doesn't seem high hanging. It's as if the fruit we pick not only nourished us but cause us to grow larger and provided seeds for new trees to boot.