Good News About Subsistence
Robin’s sounding strangely like a doom-sayer* lately:
But as long as enough people are free to choose their fertility… then in the long run we should expect to see a substantial
fraction of population with an heritable inclination to double their
population at least every century. So if overall economic growth
doubles less than every century, as I’ve argued
it simply must in the long run, income per capital must fall over the
long run, a fall whose only fundamental limit is subsistence; we can’t
have kids if we can’t afford them.
For flesh-and-blood lives, as opposed to vivid simulations, I actually agree with Robin. But there are important – and heartening – caveats that I think (?) he accepts, but isn’t pushing:
1. The fact that repeatedly doubling the human population will eventually reduce per-capita income does not show vastly increasing it would reduce per-capita income. As I said before:
“It has to stop sometime” was as true when our population was 10,000 as
it is today. But as far as we can tell from the simultaneous rise of
population and per-capita income, “sometime” is a long way off.
2. As Landsburg has argued, if you don’t like your family’s per-capita income, you can unilaterally raise it by having fewer kids. If you’re worried that your neighbors’ breeding is reducing your kids’ expected wages, take the money you saved by having fewer kids, and set up a trust on their behalf. Just make sure that the trust invests in capital, land, and/or other assets that go up in value as population rises.
Of course Robin could point out that in the long-run, people who use these strategies will become a small fraction of the population. True enough. But the total number of descendants of less fertile people doesn’t have to decline over time. As long as your dynasty doesn’t fall below replacement, following my proposed strategy implies merely that your descendants will be increasingly outnumbered, not that they’ll go extinct.
3. You have to be careful with the word “subsistence.” It’s true that eventually the relative price of kids will be so high that the average person will only be able to physically sustain two. But people in this “subsistence” regime could still have awesome entertainment, art, science, blogs, virtual reality, and so on. The relative price of fitness-reducing consumption will fall over time. Implication: In Robin’s seemingly frightening scenario, anyone willing to forego a child could consume a massive bundle of fun stuff instead.
In short, the best way to explain Robin’s claim isn’t that our descendants will be “forced” to slave day and night to feed hungry mouths. Rather, it’s that our descendants will care a lot more about kids than we do. However, if one of your quirky descendants wants a different kind of life, it will still be well within his budget set.
* As far as I understand, Robin cares about aggregate, not per-capita welfare. So he would deny that he’s being a doom-sayer.