My claims are mostly about median income, not average. I am not making strong 99.9% confident claims; I am making my best estimates. So even if I cannot prove that any future physics will limit economic value per atom, I can use our best understanding of physics today to estimate such limits.
Strong security might allow high median income in the nations that limit population, but that would not assure the global median remained high.
On your capital argument, I think you need to learn more econ growth theory.
Your meme argument would apply to any non-meme-pushing use of resources whatsoever. And why can't having kids be a good way to push memes?
The demarcation of distinct "capita" for purposes of "per capita" wealth offers a lot of room for flexibility. If we assess wealth on a per-cell basis (in energy, food, etc), then human wealth is comparable to bacterial wealth within a couple orders of magnitude by some metrics. But if we assess at the level of an 'organism' human wealth is astronomically greater.
Future intelligences may demarcate identity in such a way that the members of the 'proletariat' are just components of 'capita,' without independent desires. Or labor might be ...
Under the theory of eternal inflation new universes keep being created at an exponentially growing rate. If we could find a way to keep sending our surplus population to different universes we could have unlimited growth.
A "world government" and "unlimited growth" I can understand.
However:
Memes are not really a solution to Malthus's dilemma. They are just a different type of substrate for inheritance. The world filling with memes might indeed prevent the world from filling up with DNA - but then you have the exact same Malthusian problem all over again with the new medium of inheritance.
The "Disease or Warfare" scenario apparently retains the essential undesirable element of Malthus's scenario of resource limitation - namely the failure of much of the population to survive to reproduce. The standard of living for those that remain could be high, though.
From what I've heard, people don't try to have as many children as possible-- they try to have as many children as will be able to inherit their niche. This could explain why those who can afford college for their children put money into that for a small number of children rather than into having as many children as possible.
We already have something like Psychohistorian's nudges. There's a lot more pressure to not leave a child home alone, and that raises the cost of raising children.
The other observed fact is that birth rates drop when women get rights....
How about simple spontaneous population stability... I live in a country with negative birth rate but the population is increasing due to immigration nevertheless. This state of affairs hasn't been legislated into existence, it just happened, and may be a natural behaviour of large human populations. Perhaps once the whole world reaches western standards of living the whole world will stop growing exponentially, with pockets of negative growth being compensated by low but positive growth in others... in the long term the trend could even be for decreasing population...
Notice how little evidence we have for most human societies in history to be really close to Malthusian population bounds.
It's really incompatible with evidence unless you take "extreme long term view" like Robin, in which case it becomes essentially non-empirical.
This is like most of the responses to Robin on OB; extreme examples of wishful thinking. None of the responses, here or there, are stable or address Robin's point that in the very long term population will probably grow until it reaches the level of subsistence.
I'd add:
Superstimuli - New technology creates activities that are so enjoyable that most people just don't bother having children, or don't want to have many children.
Default birth control - all individuals (of at least one gender) are implanted with effective birth control at birth/onset of puberty. It's easy to turn off, and anyone who wants to turn it off can, but you can't conceive without taking making an affirmative decision to do so. This could lower birthrates enough to hit replacement.
Nudges - like default birth control, but through other mechanis...
Population doubling takes place in alternative branches of a coherent quantum superposition, so that each single branch has plenty of capital. Parents don't get to talk to their children much, but everyone maintains a higher standard of living - in exchange, perhaps, for lower measure.
"Singleton
A world government or superpower imposes a population control policy over the whole world."
If predicting the far future is very difficult, why should "future people will be very rich" be different from "future people will be very poor"? Shouldn't it be just as hard to be sure of one as the other?
The big one:
Memetic instability, aka Hanson's assumptions are just wrong.
It's quite easy for an armchair evolutionary psychologist to say, "X group reproduces more than not-X. Therefore, by 2150, everyone will be Mormon because they'll be selected for!" Yes, I'm exaggerating a bit, but the actual argument is about as absurd. There aren't any large population subgroups with extremely high fertility as a subcultural norm. Given the substantial hedonistic sacrifice involved in high fertility, this is not surprising. It seems unlikely, barring kids b...
Also: Nothing. We'll be fine.
Hanson's assumptions require extremely strong memetic stability, or at least high and consistent prevalence for high-fertility. Since fertility, at the relevant margin, seems principally memetic (rather than genetic), this seems unlikely, particularly if it entails a significant sacrifice of material well-being. If it doesn't require a significant sacrifice of material well-being, then it will not likely coincide with falling standards of living. In other words, when it becomes clear that the next generation will be worse off t...
[My knowledge of High Medieval period is based mostly on listening to TTC's audiobook lecture series about it (highly recommended), not on Wikipedia.]
A few random thoughts:
I don't have one big mathematically pretty theory here. (Short-term) Malthusian theory seems to be widely accepted because it's mathematically pretty, and something like it works on many animal populations. It's not obvious from either theoretical or empirical point of view it makes sense for humans, at least after they stopped hunting and gathering own food.
Actual food production must cover actual population no matter if Malthusian hypothesis is true or not - if food production was too low, people would die; if food production was too high, there would be nobody to eat it (unless people do something funny with their food instead of eating it). So that's the wrong thing to look at. Lower population levels must automatically mean lower land area used, or lower productivity/intensity of agriculture. And we can guess people would use the "best" lands, and leave "worse" lands unused.
I think failure of Medieval Europe to rebound back to Roman population levels is much bigger problem for Malthusian theory than Tuscany's. Small highly urbanized regions like Tuscany might have simply imported food from other regions. Such explanations won't work for an entire continent.
TTC lectures present as well-established fact that quality of life increased a lot in High Medieval period, while population roughly doubled. The lecturer finds it quite puzzling, as it conflicts with Malthusian theory.
Wikipedia says that during the entire Medieval period, "land was plentiful while labour to clear and work the land was scarce". This is highly un-Malthusian scenario. Malthusian theory strongly predicts having large excess of labour.
Obviously there must be something that limits fertility. Malthusian theory says it must be potential food production, and that every land that can produce enough food to support people farming it must be used. If the mechanism is something else, we might have highly non-Malthusian (non-poor) equilibria. Wars, and failure to organize expansion to new lands (what in agricultural societies might require significant up-front investment, it definitely did in Medieval Europe, settlers on new lands were freed from usual taxes for many years) are a few obvious mechanisms.
Wikipedia says position of peasants in Western Europe which had high labour-to-land ratios was much better than in Eastern Europe with high land-to-labour ratios. Malthusian theory predicts otherwise. I can see no differences in agricultural technology, or land productivity, or anything else to explain this away.
Increase in wages after Black Death can as easily be interpreted as inflation, not as increase in gdp per capita, as prices seem to have increased correspondingly. It's not really surprising, as supply of metal money stayed constant, so supply of money per capita increased proportionally to loss of population.
Wikipedia says that Black Death had negative effects on the economy:
Economic historians like Fernand Braudel have concluded that Black Death exacerbated a recession in the European economy that had been under way since the beginning of the century.
We have really crappy data about economic history.
One issue to keep in mind is measuring wealth in calories and in other terms. People interested in malthusian theories focus on calories, while those interested in the advance of civilization may measure it in, for example, cloth. The malthusian theory predicts that the proportion of salary that goes to food should creep up in peacetime. But the advance of cities in the high medieval period made other products cheaper. When Braudel talks about economic recession, he's probably talking about abandonment of cities, which is not necessarily relevant to the ma...
This is an attempt to list all of the possible ways in which humanity may avoid scenarios where the average standard of living is close to subsistence, in response to Robin Hanson's recent series of posts on Overcoming Bias, where he argues that such an outcome is likely in the long run.
I'll start with six, some suggested by myself, and others collected from comments on Overcoming Bias and Robin's own posts. If anyone provides additional ideas, I'll add them to the list.
(I have a more general point here, BTW, which is that predicting the far future is very difficult. Before thinking that some outcome is inevitable or highly likely, it's a good idea to repeatedly ask oneself "This is all the ways that I can think of why it may fail to come true. Am I sure that all of them have low probability and that I'm not missing anything?" There may be some scenario with a non-negligible probability that your brain simply overlooked when you first asked it.)
Singleton
A world government or superpower imposes a population control policy over the whole world.
Strong Security
Strong defensive technologies and doctrines (such as Mutually Assured Destruction) allow nations, communities, and maybe tribes and families to unilaterally limit their populations within their own borders, while holding off hordes of would-be invaders and immigrants.
Non-Human Capital
Maximizing the wealth and power of a nation requires an optimal mix of human and non-human capital. Nations that fail to adopt population controls find their relative wealth and power fade over time as their mixes deviate from the optimum (i.e., they find themselves spending too much resources on raising humans, and not enough on building machines), and either move to correct this or are taken over by stronger powers. (I believe that historically this was the reason China adopted its one-child policy.)
Unlimited Growth
We don't completely understand the laws of physics, nor the nature of value. There turns out to be some way for economic growth to continue without limit. (Robin himself once wrote "I know of no law limiting economic value per atom" but apparently changed his mind later.)
Selfish Memes
Memes that manage to divert people's resources away from biological reproduction and towards memetic reproduction will have an advantage over memes that don't. On the other hand, genes that manage to block such memes will have an advantage over genes that don't. Memes manage to keep the upper hand in this struggle (or periodically regain the upper hand).
Disease, Warfare, Natural Disasters, Aliens, Keeper of the Simulation
One or more of these come along regularly to keep the human population in check and per capita incomes above subsistence.