[ Question ]

How large can the solar system's economy get?

by WilliamKiely1 min read1st Jul 20217 comments


Long-term futureEconomic growthEconomics

In Open Philanthropy's Report on Whether AI Could Drive Explosive Economic Growth, Tom Davidson writes:

Overall, I place at least 10% probability on advanced AI driving explosive growth [30% GWP growth each year] this century.

While I'm not aware of anyone claiming that if such 30% annual GWP growth were to occur that the economy would continue to grow at that rate for many years, it occurred to me that at that rate of growth the economy would grow by a factor of 10^11 each century.

At that rate of growth the solar system's economy would reach its maximum size (imposed by the amount of matter in the solar system and how efficiently that matter can be used) very quickly, probably within about a century or two.

This leads me to wonder, what exactly is the maximum size economy the solar system can sustain? Are there existing published estimates on this question?

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3 Answers

It is clear that energy consumption cannot continue to grow exponentially for much more than 1000 years. But it might be argued that we can continue to extract ever more economic value from less and less energy, especially with VR. This is discussed in the debate between Robin Hanson and Bryan Caplan, and Toby Ord in the comments. 

See the comment here by Max Daniel:

"there are limits in how much value (whether in an economic or moral sense) we can produce per unit of available energy, and (ii) we will eventually only be able to expand the total amount of available energy subexponentially (there can only be so much stuff in a given volume of space, and the amount of available space is proportional to the speed of light cubed - polynomial rather than exponential growth).



In 275, 345, and 400 years, [assuming current growth rates of global power demand] we demand all the sunlight hitting land and then the earth as a whole, assuming 20%, 100%, and 100% conversion efficiencies, respectively. In 1350 years, we use as much power as the sun generates. In 2450 years, we use as much as all hundred-billion stars in the Milky Way galaxy.

(Tom Murphy)


In Holden Karnofsky's just-published Cold Takes blog post This Can't Go On, he cites how at 2% annual economic growth the economy would grow by a factor of 3*10^70 in just 8,200 years. Since there are likely fewer than that many atoms in our galaxy, this would mean that "we'd need to be sustaining multiple economies as big as today's entire world economy per atom." Holden says:

Is it imaginable that we could develop the technology to support multiple equivalents of today's entire civilization, per atom available? Sure - but this would require a radical degree of transformation of our lives and societies, far beyond how much change we've seen over the course of human history to date. And I wouldn't exactly bet that this is how things are going to go over the next several thousand years.

It seems much more likely that we will "run out" of new scientific insights, technological innovations, and resources, and the regime of "getting richer by a few percent a year" will come to an end. After all, this regime is only a couple hundred years old.

(Edited 8/3 to include the written post quote now that it's published, rather than my transcription of the audio)

Is... this post published yet? I can't find it anywhere.

2WilliamKiely6moIt is published now (here [https://www.cold-takes.com/this-cant-go-on/], but wasn't at the time of my above comment. The audio was published before the written post (by about a day-ish). I sent Holden the feedback to let him know.