A few months after writing this post I realized that one of the key arguments was importantly flawed. I therefore recommend against inclusion in the 2019 review. This post presents an improved version of the original argument, explains the flaw, and then updates my all-things-considered view accordingly.

Improved version of my original argument

1. Definitions:
   1. “Soft takeoff” is roughly “AI will be like the Industrial Revolution but 10x-100x faster”
   2. “Decisive Strategic Advantage” (DSA) is “a level of technological and other advantages sufficient to enable it to achieve complete world domination.” In other words, DSA is roughly when one faction or entity has the capability to “take over the world.” (What taking over the world means is an interesting question which we won’t explore here. Nowadays I’d reframe things in terms of potential PONRs.)
   3. We ask how likely it is that DSA arises, conditional on soft takeoff. Note that DSA does not mean the world is actually taken over, only that one faction at some point has the ability to do so. They might be too cautious or too ethical to try. Or they might try and fail due to bad luck.
2. In a soft takeoff scenario, a 0.3 - 3 year technological lead over your competitors probably gives you a DSA.
   1. It seems plausible that for much of human history, a 30-year technological lead over your competitors was not enough to give you a DSA.
   2. It also seems plausible that during and after the industrial revolution, a 30-year technological lead was enough. (For more arguments on this key point, see my original post.)
   3. This supports a plausible conjecture that when the pace of technological progress speeds up, the length (in clock time) of technological lead needed for DSA shrinks proportionally.
3. So a soft takeoff could lead to a DSA insofar as there is a 0.3 - 3 year lead at the beginning which is maintained for a few years.
4. 0.3 - 3 year technological leads are reasonably common today, and in particular it’s plausible that there could be one in the field of AI research.
5. There’s a reasonable chance of such a lead being maintained for a few years.
   1. This is a messy question, but judging by the table below, it seems that if anything the lead of the front-runner in this scenario is more likely to lengthen than shorten!
   2. If this is so, why did no one achieve DSA during the Industrial Revolution? My answer is that spies/hacking/leaks/etc. are much more powerful during the industrial revolution than they are during a soft takeoff, because they have an entire economy to steal from and decades to do it, whereas in a soft takeoff ideas can be hoarded in a specific corporation and there’s only a few years (or months!) to do it.
6. Therefore, there’s a reasonable chance of DSA conditional on soft takeoff.

I take it that 2, 4, and 5 are the controversial bits. I still stand by 2, and the arguments made for it in my original post. I also stand by 4. (To be clear, it’s not like I’ve investigated these things in detail. I’ve just thought about them for a bit and convinced myself that they are probably right, and I haven’t encountered any convincing counterarguments so far.)

5 is where I made a big mistake. 

(Comments on my original post also attacked 5 a lot, but none of them caught the mistake as far as I can tell.)

My big mistake

Basically, my mistake was to conflate leads measured in number-of-hoarded-ideas with leads measured in clock time. Clock-time leads shrink automatically as the pace of innovation speeds up, because if everyone is innovating 10x faster, then you need 10x as many hoarded ideas to have an N-year lead. 

Here’s a toy model, based on the one I gave in the original post:

There are some projects/factions. There are many ideas. Projects can have access to ideas. Projects make progress, in the form of discovering (gaining access to) ideas. For each idea they access, they can decide to hoard or not-hoard it. If they don’t hoard it, it becomes accessible to all. Hoarded ideas are only accessible by the project that discovered them (though other projects can independently rediscover them). The rate of progress of a project is proportional to how many ideas they can access.

Let’s distinguish two ways to operationalize the technological lead of a project. One is to measure it in ideas, e.g. “Project X has 100 hoarded ideas and project Y has only 10, so Project X is 90 ideas ahead.” But another way is to measure it in clock time, e.g. “It’ll take 3 years for project Y to have access to as many ideas as project X has now.” 

Suppose that all projects hoard all their ideas. Then the ideas-lead of the leading project will tend to lengthen: the project begins with more ideas, so it makes faster progress, so it adds new ideas to its hoard faster than others can add new ideas to theirs. However, the clocktime-lead of the leading project will remain fixed. It’s like two identical cars accelerating one after the other on an on-ramp to a highway: the distance between them increases, but if one entered the ramp three seconds ahead, it will still be three seconds ahead when they are on the highway.

But realistically not all projects will hoard all their ideas. Suppose instead that for the leading project, 10% of their new ideas are discovered in-house, and 90% come from publicly available discoveries accessible to all. Then, to continue the car analogy, it’s as if 90% of the lead car’s acceleration comes from a strong wind that blows on both cars equally. The lead of the first car/project will lengthen slightly when measured by distance/ideas, but shrink dramatically when measured by clock time.

The upshot is that we should return to that table of factors and add a big one to the left-hand column: Leads shorten automatically as general progress speeds up, so if the lead project produces only a small fraction of the general progress, maintaining a 3-year lead throughout a soft takeoff is (all else equal) almost as hard as growing a 3-year lead into a 30-year lead during the 20th century. In order to overcome this, the factors on the right would need to be very strong indeed.

Conclusions

My original argument was wrong. I stand by points 2 and 4 though, and by the subsequent posts I made in this sequence. I notice I am confused, perhaps by a seeming contradiction between my explicit model here and my take on history, which is that rapid takeovers and upsets in the balance of power have happened many times, that power has become more and more concentrated over time, and that there are not-so-distant possible worlds in which a single man rules the whole world sometime in the 20th century. Some threads to pull on:

1. To the surprise of my past self, Paul agreed DSA is plausible for major nations, just not for smaller entities like corporations: “I totally agree that it wouldn't be crazy for a major world power to pull ahead of others technologically and eventually be able to win a war handily, and that will tend happen over shorter and shorter timescales if economic and technological progress accelerate.”) Perhaps we’ve been talking past each other, because I think a very important point is that it’s common for small entities to gain control of large entities. I’m not imagining a corporation fighting a war against the US government; I’m imagining it taking over the US government via tech-enhanced lobbying, activism, and maybe some skullduggery. (And to be clear, I’m usually imagining that the corporation was previously taken over by AIs it built or bought.)
2. Even if takeoff takes several years it could be unevenly distributed such that (for example) 30% of the strategically relevant research progress happens in a single corporation. I think 30% of the strategically relevant research happening in a single corporation at beginning of a multi-year takeoff would probably be enough for DSA.
3. Since writing this post my thinking has shifted to focus less on DSA and more on potential AI-induced PONRs. I also now prefer a different definition of slow/fast takeoff. Thus, perhaps this old discussion simply isn’t very relevant anymore.
4. Currently the most plausible doom scenario in my mind is maybe a version of Paul’s Type II failure. (If this is surprising to you, reread it while asking yourself what terms like “correlated automation failure” are euphemisms for.) I’m not sure how to classify it, but this suggests that we may disagree less than I thought.

Thanks to Jacob Laggeros for nudging me to review my post and finally get all this off my chest. And double thanks to all the people who commented on the original post!